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Page No 94:

Question 1:

The distance of the point P(2, 3) from the x-axis is
(a) 2
(b) 3
(c) 1
(d) 5

Answer:

A point P is given with coordinates (2, 3).

The distance of a point from the x-axis is given by its y-coordinate. Thus, the distance of point P(2, 3) from the x-axis is 3 units.

Hence, the correct answer is option (b).

Page No 94:

Question 2:

AOBC is a rectangle whose three vertices are A(0, 3), O(0, 0) and B(5, 0). The length of its diagonal is
(a) 5
(b) 3
(c) 34
(d) 4

Answer:

Given that, AOBC is a rectangle with vertices A(0, 3), O(0, 0) and B(5, 0).

Length of the diagonal AB = Distance between the points A(0,3) and B(5,0)

Now,
Distance between the points (x1y1) and (x2y2) = d=x2-x12+y2-y12

Thus,
AB=5-02+0-32=25+9=34

Hence, the correct answer is option (c).
 

Page No 94:

Question 3:

The points (–4, 0), (4, 0) and (0, 3) are the vertices of a
(a) right triangle
(b) isosceles triangle
(c) equilateral triangle
(d) scalene triangle

Answer:

Given that, the three points A(–4, 0), B(4, 0) and C(0, 3) are the vertices of a triangle and we have to determine the type of triangle formed by them.

Distance between the points (x1y1) and (x2y2) = d=x2-x12+y2-y12

AB=4--42+0-02=82=8

BC=0-42+3-02=16+9=25=5

CA=0--42+3-02=16+9=25=5

Thus, two sides of the triangle are equal, which means it is an isosceles triangle.

Hence, the correct answer is option (b).



Page No 95:

Question 4:

The point which lies on the perpendicular bisector of the line segment joining the points A(–2, –5) and B(2, 5) is
(a) (0, 0)
(b) (0, 2)
(C) (2, 0)
(d) (–2,0)

Answer:

Given that, a line segment is formed by joining the points A(–2, –5) and B(2, 5). The perpendicular bisector of a line segment passes through its mid-point.

Let C be the point of the line segment AB through which its perpendicular bisector passes. Thus, point C is the mid-point of AB, i.e., it divides the line segment in the ratio 1 : 1.

Coordinates of C=x1+x22,y1+y22=-2+22,-5+52=0,0

Hence, the correct answer is option (a).
 

Page No 95:

Question 5:

Two fourth vertex D of a parallelogram ABCD whose three vertices are A(–2, 3), B(6, 7) and C(8, 3) is
(a) (0, 1)
(b) (0, –1)
(c) (–1, 0)
(d) (1, 0)

Answer:

Given that, a parallelogram ABCD has three vertices as A(–2, 3), B(6, 7) and C(8, 3).

The diagonals of a parallelogram bisect each other. So, the mid-point of AC is same as the mid-point of BD. Let the point of intersection of AC and BD be O.

Therefore, the coordinates of O (or mid-point of AC) are given as:
Coordinates of O=x1+x22,y1+y22=8-22,3+32=3,3

Let the coordinates of D be (x, y).
Then,
Mid-point of BD=3,33,3=6+x2,7+y2x=0 and y=-1

Hence, the correct answer is option (b).

Page No 95:

Question 6:

The coordinates of the point which is equidistant from the vertices O(0, 0), A(2x, 0) and B(0, 2y) of triangle OAB are
(a) (x, y)
(b) (y, x)
(c) x2,y2
(d) y2,x2

Answer:

Given that, O(0, 0), A(2x, 0) and B(0, 2y) are the vertices of triangle OAB. This is a right angled triangle as two vertices are on the coordinate axes and the third one is the origin, thus making a right angle at the origin.

For a right triangle, the circumcentre is the mid-point of the hypotenuse. ​The point which is equidistant from vertices of triangle is termed as circumcentre of that triangle.

Here, the end-points of the hypotenuse are A(2x, 0) and B(0, 2y). Let the mid-point of AB be C.

So,
Coordinates of C=2x+02,0+2y2                      Coordinates of the mid-point=x1+x22,y1+y22=2x2,2y2=x,y

Hence, the correct answer is option (a).

Page No 95:

Question 7:

A circle drawn with origin as the centre passes through 132,0. The point which does not lie in the interior of the circle is
(a) -34,1
(b) 2,73
(c) 5,-12
(d) -6,52

Answer:

Given that, a circle is drawn with origin as the centre passes through the point A132,0.

The radius of the circle is equal to the distance between the centre O(0, 0) and A132,0.

Now,
OA=x2-x12+y2-y12                   Distance between two points x1,y1 and x2,y2= x2-x12+y2-y12=132-02+0-02=1322=132=6.5 units

A point lies inside, on or outside the circle if the distance of the point from the centre of the circle is less than, equal to or greater than the radius of the circle respectively.

The points -34,12,73 and 5,-12 seem to lie inside the circle with radius 6.5 units. So, consider the distance between O(0, 0) and point D-6,52.

OD=x2-x12+y2-y12                   Distance between two points x1,y1 and x2,y2= x2-x12+y2-y12=-6-02+52-02=36+254=1694=132=6.5 units

Thus, point D lies on the circle and not in its interior.

Hence, the correct answer is option (d).

Page No 95:

Question 8:

If the distance between the points (4, p) and (1, 0) is 5, then the value of p is
(a) 4 only
(b) ±4
(c) −4, only
(d) 0

Answer:

It is given that distance between (4, p) and (1, 0) is 5.

In general, the distance between A and B is given by .

So,

On further simplification,

Hence, the correct answer is option (b).

Page No 95:

Question 9:

The points A(9, 0), B(9, 6), C(–9, 6) and D(–9, 0) are the vertices of a
(a) square
(b) rectangle
(c) rhombus
(d) trapezium

Answer:

Given that, the vertices of a quadrilateral are A(9, 0), B(9, 6), C(–9, 6) and D(–9, 0).

The distance between two points with coordinates x1,y1 and x2,y2 is given as d=x2-x12+y2-y12.

Here,
AB=9-92+6-02=6 units

BC=-9-92+6-62=-182=18 units

CD=-9+92+0-62=-62=6 units

DA=-9-92+0-02=-182=18 units

Since the opposite sides are equal, it is a rectangle.

Hence, the correct answer is option (b).

Page No 95:

Question 10:

If the distance between the points (2, –2) and (–1, x) is 5, then the sum of the values of x is
(a) 4
(b) –4
(c) 8
(d) –8

Answer:

Given that, the distance between two points A(2, –2) and B(–1, x) is 5.

The distance between two points with coordinates x1,y1 and x2,y2 is given as d=x2-x12+y2-y12.

Here,
5=-1-22+x+225=9+x2+4x+425=x2+4x+13x2+4x-12=0x2+6x-2x-12=0xx+6-2x+6=0x-2x+6=0x=2 or x=-6

Thus, the values of x are 2 or -6.

Therefore, the sum of the values of x-4.

Hence, the correct answer is option (b).

Page No 95:

Question 11:

Mark the correct alternative in each of the following:

The distance between the points (cos θ, 0) and (sin θ − cos θ) is

(a) 3

(b) 2

(c) 2

(d) 1

Answer:

We have to find the distance between and.

In general, the distance between A and B is given by,

So,

But according to the trigonometric identity,

Therefore,

So, the answer is (b)

Page No 95:

Question 12:

The distance between the points (a cos 25°, 0) and (0, a cos 65°) is

(a) a

(b) 2a

(c) 3a

(d) None of these

Answer:

We have to find the distance between A(a cos 25°, 0)  and.

In general, the distance between A and B is given by,

So,

 AB=0-acos25°2+acos65°-02=acos25°2+acos65°2

cos25°=sin65° and cos65°=sin25°

But according to the trigonometric identity,

Therefore,

So, the answer is (a)

Page No 95:

Question 13:

If x is a positive integer such that the distance between points P (x, 2) and Q (3, −6) is 10 units, then x =

(a) 3

(b) −3

(c) 9

(d) −9

Answer:

It is given that distance between P (x, 2) and is 10.

In general, the distance between A and B is given by,

So,

On further simplification,

We will neglect the negative value. So,

So the answer is (c)

Page No 95:

Question 14:

The distance between the points (a cos θ + b sin θ, 0) and (0, a sin θ − b cos θ) is

(a) a2 + b2

(b) a + b

(c) a2 − b2

(d) a2 + b2

Answer:

We have to find the distance between and.

In general, the distance between A and B is given by,

So,

But according to the trigonometric identity,

Therefore,

So, the answer is (d)

Page No 95:

Question 15:

If the distance between the points (4, p) and (1, 0) is 5, then p =
(a) ±4
(b) 4
(c) –4
(d) 0

Answer:

Given that, the distance between two points A(4, p) and B(1, 0) is 5.

The distance between two points with coordinates x1,y1 and x2,y2 is given as d=x2-x12+y2-y12.

Here,
5=1-42+0-p25=9+p225=p2+9p2-16=0p=±4

Hence, the correct answer is option (a).

Page No 95:

Question 16:

A line segment is of length 10 units. If the coordinates of its one end are (2, −3) and the abscissa of the other end is 10, then its ordinate is

(a) 9, 6

(b) 3, −9

(c) −3, 9

(d) 9, −6

Answer:

It is given that distance between P (2,−3) and is 10.

In general, the distance between A and B is given by,

So,

On further simplification,

We will neglect the negative value. So,

So the answer is (b)

Page No 95:

Question 17:

The perimeter of the triangle formed by the points (0, 0), (0, 1) and (0, 1) is

(a) 1 ± 2

(b) 2 + 1

(c) 3

(d) 2+2

Answer:

We have a triangle whose co-ordinates are A (0, 0); B (1, 0); C (0, 1). So clearly the triangle is right angled triangle, right angled at A. So,

Now apply Pythagoras theorem to get the hypotenuse,

So the perimeter of the triangle is,

Therefore the answer is (d)

Page No 95:

Question 18:

If A (2, 2), B (−4, −4) and C (5, −8) are the vertices of a triangle, than the length of the median through vertex C is

(a) 65

(b) 117

(c) 85

(d) 113

Answer:

We have a triangle in which the co-ordinates of the vertices are A (2, 2) B (−4,−4) and C (5,−8).

In general to find the mid-point of two points and we use section formula as,

Therefore mid-point D of side AB can be written as,

Now equate the individual terms to get,

So co-ordinates of D is (−1,−1)

So the length of median from C to the side AB,

So the answer is (c)

Page No 95:

Question 19:

If A(x, 2), B(–3, –4) and C(7, –5) are collinear, then the value of x is
(a) –63
(b) 63
(c) 60
(d) –60

Answer:

Given that, the three points A(x, 2), B(–3, –4) and C(7, –5) are collinear.

The distance between two points with coordinates x1,y1 and x2,y2 is given as d=x2-x12+y2-y12.

Here,
AB=-3-x2+-4-22=9+x2+6x+36=x2+6x+45

BC=7+32+-5+42=100+1=101

CA=7-x2+-5-22=49+x2-14x+49=x2-14x+98

If they are collinear, then AB + BC = CA.
Thus,
x2+6x+45+101=x2-14x+98

Squaring both sides,
x2+6x+45+101+2101x2+606x+4545=x2-14x+98
20x+48+2101x2+606x+4545=0
10x+24=-101x2+606x+4545

Squaring both sides,
100x2+576+480x=101x2+606x+4545x2+126x+3969=0x+63x+63=0

Thus, the value of x is –63.

Hence, the correct answer is option (a).



Page No 96:

Question 20:

The line segment joining points (−3, −4), and (1, −2) is divided by y-axis in the ratio

(a) 1 : 3

(b) 2 : 3

(c) 3 : 1

(d) 2 : 3

Answer:

Let P be the point of intersection of y-axis with the line segment joining A (−3,−4) and B (1,−2) which divides the line segment AB in the ratio.

Now according to the section formula if point a point P divides a line segment joining and in the ratio m:n internally than,

Now we will use section formula as,

Now equate the x component on both the sides,

On further simplification,

So y-axis divides AB in the ratio

So the answer is (c)

Page No 96:

Question 21:

If points (t, 2t), (−2, 6) and (3, 1) are collinear, then t =

(a) 34

(b) 43

(c) 53

(d) 35

Answer:

We have three collinear points.

In general if are collinear then,

So,

So,

So,

Therefore,

So the answer is (b)

Page No 96:

Question 22:

If the points A(3, 1) B(5, p) and C(7, −5) are collinear, then
(a) −2
(b) 2
(c) −1
(d) 1

Answer:

We have three collinear points A(3, 1) B(5, p) and C(7, −5).

In general, if are collinear then, the area of the triangle = 0. 
i.e., 

Here, x1=3, y1=1, x2=5, y2=p, x3=7, y3=-5,
So,

3p+5+5-5-1+71-p=03p+15-30+7-7p=0-4p-8=0p=-2

Hence, the correct answer is option (a).

Page No 96:

Question 23:

If (x , 2), (−3, −4) and (7, −5) are collinear, then x =

(a) 60

(b) 63

(c) −63

(d) −60

Answer:

We have three collinear points.

In general if are collinear then,

So,

So,

Therefore,

So the answer is (c)

Page No 96:

Question 24:

The ratio in which (4, 5) divides the join of (2, 3) and (7, 8) is

(a) −2 : 3

(b) −3 : 2

(c) 3 : 2

(d) 2 : 3

Answer:

The co-ordinates of a point which divided two points and internally in the ratio is given by the formula,

Here it is said that the point (4, 5) divides the points A(2,3) and B(7,8). Substituting these values in the above formula we have,

Equating the individual components we have,

Hence the correct choice is option (d).

Page No 96:

Question 25:

 The ratio in which the x-axis divides the segment joining (3, 6) and (12, −3) is

(a) 2: 1

(b) 1 : 2

(c) −2 : 1

(d) 1 : −2

Answer:

Let P be the point of intersection of x-axis with the line segment joining A (3, 6) and B (12, −3) which divides the line segment AB in the ratio.

Now according to the section formula if point a point P divides a line segment joining   andin the ratio m: n internally than,

Now we will use section formula as,

Now equate the y component on both the sides,

On further simplification,

So x-axis divides AB in the ratio

So the answer is (a)

Page No 96:

Question 26:

If points (1, 2), (–5, 6) and (a, –2) are collinear, then a =
(a) –3
(b) 7
(c) 2
(d) –2

Answer:

Given that, the three points A(1, 2), B(–5, 6) and C(a, –2) are collinear.

The distance between two points with coordinates x1,y1 and x2,y2 is given as d=x2-x12+y2-y12.

Here,
AB=-5-12+6-22=36+16=52

BC=a+52+-2-62=a2+25+10a+64=a2+10a+89

CA=1-a2+2+22=a2+1-2a+16=a2-2a+17

If they are collinear, then AB + BC = CA.

Thus,
52+a2+10a+89=a2-2a+17

Squaring both sides,
52+a2+10a+89+252a2+520a+4628=a2-2a+1712a+124+252a2+520a+4628=0

Squaring both sides,
6a+62=-52a2+520a+462836a2+3844+744a=52a2+520a+462816a2-224a+784=0a2-14a+49=0a2-7a-7a+49=0a-7a-7=0a=7

Hence, the correct answer is option (b).

Page No 96:

Question 27:

The distance of the point (4, 7) from the x-axis is

(a) 4

(b) 7

(c) 11

(d) 65

Answer:

The ordinate of a point gives its distance from the x-axis.

So, the distance of (4, 7) from x-axis is

So the answer is (b)

Page No 96:

Question 28:

The distance of the point (4, 7) from the y-axis is

(a) 4

(b) 7

(c) 11

(d) 65

Answer:

The distance of a point from y-axis is given by abscissa of that point.

So, distance of (4, 7) from y-axis is.

So the answer is (a)

 

Page No 96:

Question 29:

The coordinates of the point P dividing the line segment joining the points A(1, 3) and B(4, 6) in the ratio 2 : 1 are
(a) (2, 4)
(b) (3, 5)
(c) (4, 2)
(d) (5, 3)

Answer:

Given that, the point P divides the line segment joining the points A(1, 3) and B(4, 6) in the ratio 2 : 1. Let the coordinates of P be (x, y).

Using the section formula, the coordinates of the point O(xy) which divides the line segment joining the points X(x1, y1) and Y(x2, y2), internally, in the ratio m1 : m2 are given by m1x2+m2x1m1+m2,m1y2+m2y1m1+m2.

Here, (x1y1) = (1, 3), (x2y2) = (4, 6) and m1 : m2 = 2 : 1

Thus,
Coordinates of P=24+112+1,26+132+1=93,153=3,5

Hence, the correct answer is option (b).
 

Page No 96:

Question 30:

The point on the x-axis which is equidistant from points (−1, 0) and (5, 0) is

(a) (0, 2)                          (b) (2, 0)                          (c) (3, 0)                          (d) (0, 3)                         [CBSE 2013]

Answer:

Let A(−1, 0) and B(5, 0) be the given points. Suppose the required point on the x-axis be P(x, 0).

It is given that P(x, 0) is equidistant from A(−1, 0) and B(5, 0).

∴ PA = PB

⇒ PA2 = PB2

x--12+0-02=x-52+0-02                           (Using distance formula)

x+12=x-52x2+2x+1=x2-10x+2512x=24x=2

Thus, the required point is (2, 0).

Hence, the correct answer is option B.

Page No 96:

Question 31:

If three points (0, 0), 3, 3 and (3, λ) form an equilateral triangle, then λ =

(a) 2

(b) −3

(c) −4

(d) None of these

Answer:

We have an equilateral triangle whose co-ordinates are A (0, 0); and.

Since the triangle is equilateral. So,

So,

Cancel out the common terms from both the sides,

Therefore,

So, the answer is (d)

Page No 96:

Question 32:

If the points (k, 2k), (3k, 3k) and (3, 1) are collinear, then k

(a) 13

(b) -13

(c) 23

(d) -23

Answer:

We have three collinear points.

In general if are collinear then, area of the triangle is 0.

So,

So,

Take out the common terms,

Therefore,

So the answer is (b)

Page No 96:

Question 33:

The coordinates of the point on X-axis which are equidistant from the points (−3, 4) and (2, 5) are

(a) (20, 0)

(b) (−23, 0)

(c) 45, 0

(d) None of these  

Answer:

Let the point be A be equidistant from the two given points P (−3, 4) and Q (2, 5).

So applying distance formula, we get,

Therefore,

Hence the co-ordinates of A are

So the answer is- (D) none of these.

Page No 96:

Question 34:

If A (5, 3), B (11, −5) and P (12, y) are the vertices of a right triangle right angled at P, then y=

(a)  −2, 4

(b) −2, −4

(c) 2, −4

(d) 2, 4

Answer:

Disclaimer: option (b) and (c) are given to be same in the book. So, we are considering option (b) as −2, −4
instead of −2, 4.

We have a right angled triangle whose co-ordinates are A (5, 3); B (11,−5);

. So clearly the triangle is, right angled at A. So,

Now apply Pythagoras theorem to get,

So,

On further simplification we get the quadratic equation as,

Now solve this equation using factorization method to get,

Therefore,

So the answer is (c)

Page No 96:

Question 35:

The area of the triangle formed by (a, b + c), (b, c + a) and (c, a + b)

(a) a + b + c

(b) abc

(c) (a + b + c)2

(d) 0

Answer:

We have three non-collinear points.

In general if are non-collinear points then are of the triangle formed is given by-

So,

So the answer is (d)

Page No 96:

Question 36:

If the area of the triangle formed by the points (x, 2x), (−2, 6)  and (3, 1) is 5 square units , then x =

(a) 23

(b) 35

(c) 3

(d) 5

Answer:

We have the co-ordinates of the vertices of the triangle aswhich has an area of 5 sq.units.

In general if are non-collinear points then area of the triangle formed is given by-,

So,

Simplify the modulus function to get,

Therefore,

So the answer is (a)

Page No 96:

Question 37:

If points (a, 0), (0, b) and (1, 1)  are collinear, then 1a+1b = 

(a) 1

(b) 2

(c) 0

(d) −1

Answer:

We have three collinear points.

In general if are collinear then,

So,

So,

Divide both the sides by,

So the answer is (a)

Page No 96:

Question 38:

If the centroid of a triangle is (1, 4) and two of its vertices are (4, −3) and (−9, 7), then the area of the triangle is

(a) 183 sq. units

(b) 1832 sq. units

(c) 366 sq. units

(d) 1834 sq. units

Answer:

We have to find the co-ordinates of the third vertex of the given triangle. Let the co-ordinates of the third vertex be.

The co-ordinates of other two vertices are (4,−3) and (−9, 7)

The co-ordinate of the centroid is (1, 4)

We know that the co-ordinates of the centroid of a triangle whose vertices are is

So,

Compare individual terms on both the sides-

So,

Similarly,

So,

So the co-ordinate of third vertex is (8, 8)

In general if are non-collinear points then are of the triangle formed is given by-,

So,

So the answer is (b)



Page No 97:

Question 39:

If the centroid of the triangle formed by (7, x) (y, −6) and (9, 10) is at (6, 3), then (x, y) =

(a) (4, 5)

(b) (5, 4)

(c) (−5, −2)

(d) (5, 2)

Answer:

We have to find the unknown co-ordinates.

The co-ordinates of vertices are

The co-ordinate of the centroid is (6, 3)

We know that the co-ordinates of the centroid of a triangle whose vertices are is

So,

Compare individual terms on both the sides-

So,

Similarly,

So,

So the answer is (d)

Page No 97:

Question 40:

If P is a point on x-axis such that its distance from the origin is 3 units, then the coordinates of a point Q on OY such that OP = OQ, are

(a) (0, 3)

(b) (3, 0)

(c) (0, 0)

(d) (0, −3)

Answer:

GIVEN: If P is a point on x axis such that its distance from the origin is 3 units.

TO FIND: The coordinates of a point Q on OY such that OP= OQ.

On x axis y coordinates is 0. Hence the coordinates of point P will be (3, 0) as it is given that the distance from origin is 3 units.

Now then the coordinates of Q on OY such that OP = OQ

On y axis x coordinates is 0. Hence the coordinates of point Q will be (0, 3)

Hence correct option is (a)

 

Page No 97:

Question 41:

If the points P (x, y) is equidistant from A (5, 1) and B (−1, 5), then

(a) 5x = y

(b) x = 5y

(c) 3x = 2y

(d) 2x = 3y

Answer:

It is given that is equidistant to the point

So,

So apply distance formula to get the co-ordinates of the unknown value as,

On further simplification we get,

So,

Thus,

So the answer is (c)

Page No 97:

Question 42:

If the centroid of the triangle formed by the points (3, −5), (−7, 4), (10, −k) is at the point (k −1), then k =

(a) 3

(b) 1

(c) 2

(d) 4

Answer:

We have to find the unknown co-ordinates.

The co-ordinates of vertices are

The co-ordinate of the centroid is

We know that the co-ordinates of the centroid of a triangle whose vertices are is-

So,

Compare individual terms on both the sides-

So the answer is (c)

Page No 97:

Question 43:

If (−2, 1) is the centroid of the triangle having its vertices at (x , 0) (5, −2),  (−8, y), then x, y satisfy the relation

(a) 3x + 8y = 0

(b) 3x − 8y = 0

(c) 8x + 3y = 0

(d) 8x = 3y

Answer:

We have to find the unknown co-ordinates.

The co-ordinates of vertices are

The co-ordinate of the centroid is (−2, 1)

We know that the co-ordinates of the centroid of a triangle whose vertices are is-

So,

Compare individual terms on both the sides-

So,

Similarly,

So,

It can be observed that (x, y) = (−3, 5) does not satisfy any of the relations 3x + 8y = 0, 3x − 8y = 0, 8x + 3y = 0 or 8x = 3y.

Page No 97:

Question 44:

The coordinates of the fourth vertex of the rectangle formed by the points (0, 0), (2, 0), (0, 3) are

(a) (3, 0)

(b) (0, 2)

(c) (2, 3)

(d) (3, 2)

Answer:

We have to find the co-ordinates of forth vertex of the rectangle ABCD.

We the co-ordinates of the vertices as (0, 0); (2, 0); (0, 3)

Rectangle has opposite pair of sides equal.

When we plot the given co-ordinates of the vertices on a Cartesian plane, we observe that the length and width of the rectangle is 2 and 3 units respectively.

So the co-ordinate of the forth vertex is

So the answer is (c).

Page No 97:

Question 45:

The ratio in which the line segment joining P (x1, y1) and Q (x2, y2) is divided by x-axis is

(a) y1 : y2

(b) −y1 : y2

(c) x1 : x2

(d) −x1 : x2

Answer:

Let C be the point of intersection of x-axis with the line segment joining and which divides the line segment PQ in the ratio.

Now according to the section formula if point a point P divides a line segment joining andin the ratio m:n internally than,

Now we will use section formula as,

Now equate the y component on both the sides,

On further simplification,

So the answer is (b)

Page No 97:

Question 46:

The ratio in which the line segment joining points A (a1, b1) and B (a2, b2) is divided by y-axis is

(a) −a1 : a2

(b) a1 : a2

(c) b1 : b2

(d) −b1 : b2

Answer:

Let P be the point of intersection of y-axis with the line segment joiningandwhich divides the line segment AB in the ratio.

Now according to the section formula if point a point P divides a line segment joining andin the ratio m:n internally than,

Now we will use section formula as,

Now equate the x component on both the sides,

On further simplification,

So the answer is (a)

Page No 97:

Question 47:

If the coordinates of one end of a diameter of a circle are (2, 3) and the coordinates of its centre are (−2, 5), then the coordinates of the other end of the diameter are

(a) (−6, 7)                           (b) (6, −7)                           (c) (6, 7)                           (d) (−6,−7)                           [CBSE 2012]

Answer:



Let O(−2, 5) be the centre of the given circle and A(2, 3) and B(x, y) be the end points of a diameter of the circle.

Then, O is the mid-point of AB.

Using mid-point formula, we have

2+x2=-2 and 3+y2=5                  

2+x=-4 and 3+y=10

x=-6 and y=7 

Thus, the coordinates of the other end of the diameter are (−6, 7).

Hence, the correct answer is option A.

Page No 97:

Question 48:

 In Fig. 14.46, the area of ΔABC (in square units) is

(a) 15                          (b) 10                          (c) 7.5                          (d) 2.5                                [CBSE 2013]

Answer:



The coordinates of A are (1, 3).

∴ Distance of A from the x-axis, AD = y-coordinate of A = 3 units

The number of units between B and C on the x-axis are 5.

∴ BC = 5 units

Now,

Area of ∆ABC = 12×BC×AD=12×5×3=152=7.5 square units

Thus, the area of ∆ABC is 7.5 square units.

Hence, the correct answer is option C.

Page No 97:

Question 49:

If A(4, 9), B(2, 3) and C(6, 5) are the vertices of ∆ABC, then the length of median through C is

(a) 5 units                      (b) 10 units                      (c) 25 units                      (d) 10 units                           [CBSE 2014]

Answer:

It is given that A(4, 9), B(2, 3) and C(6, 5) are the vertices of ∆ABC.



Let CD be the median of ∆ABC through C. Then, D is the mid-point of AB.

Using mid-point formula, we get

Coordinates of D = 4+22,9+32=62,122=3, 6

∴ Length of the median, AD

=6-32+5-62                Using distance formula=32+-12=10 units

Thus, the length of the required median is 10 units.

Hence, the correct answer is option B.

Page No 97:

Question 50:

If P(2, 4), Q(0, 3), R(3, 6) and S(5, y) are the vertices of a parallelogram PQRS, then the value of y is

(a) 7                             (b) 5                             (c) −7                             (d) −8                                  [CBSE 2014]

Answer:

It is given that P(2, 4), Q(0, 3), R(3, 6) and S(5, y) are the vertices of a parallelogram PQRS.



Join PR and QS, intersecting each other at O.

We know that the diagonals of the parallelogram bisect each other. So, O is the mid-point of PR and QS.

Coordinates of mid-point of PR = 2+32,4+62=52,102=52,5

Coordinates of mid-point of QS = 0+52,3+y2=52,3+y2

Now, these points coincides at the point O.

52,3+y2=52,53+y2=53+y=10y=7

Thus, the value of y is 7.

Hence, the correct answer is option A.

Page No 97:

Question 51:

The perimeter of a triangle with vertices (0, 4), (0, 0) and (3, 0) is

(a) 7 + 5                            (b) 5                            (c) 10                            (d) 12                [CBSE 2014]

Answer:

Let A(0, 4), O(0, 0) and B(3, 0) be the vertices of ∆AOB.

Using distance formula, we get

OA = 0-02+4-02=16=4 units

OB = 3-02+0-02=9=3 units

AB = 3-02+0-42=9+16=25=5 units

∴ Perimeter of ∆AOB = OA + OB + AB = 4 + 3 + 5 = 12 units

Thus, the required perimeter of the triangle is 12 units.

Hence, the correct answer is option D.



Page No 98:

Question 52:

If the point  P (2, 1 ) lies on the line segment joining points A (4,20 and B (8, 4) , then 
(a) AP = 13AB        (b) AP = BP        (C) PB13AB       (D) AP = 12AB  

Answer:

Use section formula for finding out the ratio in which P divided the line segment AB.
2,1=m18+m24m1+m2,m14+m22m1+m22=8m1+4m2m1+m2  ;  1=4m1+2m2m1+m23m1+m2=0m1m2=-13the point P divided AB in ration 1: 3 externally.AP:PB=1:3AP:AB=1:2AP=12AB

Page No 98:

Question 53:

If the point (k, 0) divides the line segment joining the points A(2, –2) and B(–7, 4) in the ratio 1 : 2, then the value of k is
(a) 1
(b) 2
(c) –2
(d) –1

Answer:

Using the Section Formula, we have
k=1×-7+2×21+2    k=-7+43   k=-33    k=-1


Hence, the correct answer is option (d).

Page No 98:

Question 54:

A line intersects the y-axis and x-axis at P and Q , respectively. If (2, -5) is the mid-point of PQ, then the coordinates of P and Q are, respectively
(a)  (0, -5) and (2, 0)          (b)  (0, 10) and (-4, 0)
(c) (0, 4) and (-10, 0 )       (d)  (0, -10) and (4 , 0)

Answer:

A line intersects the y axis, then the coordinates of P are (0, y) and x axis then the coordinates are Q(x, 0).
Therefore by section formula,
x+02,0+y2=2,-5x2,y2=2,-5x2=2, y2=-5x=4, y=-10

Hence the coordinates of P are (0, −10) and that of Q are (4, 0).

Page No 98:

Question 55:

If the points(x, 4) lies on a circle whose centre is at the origin and radius is 5, then x =

(a) ±5

(b) ±3

(c) 0

(d) ±4

Answer:

It is given that the point A(x, 4) is at a distance of 5 units from origin O.

So, apply the distance formula to get,

Therefore,

So,

So the answer is (b)

Page No 98:

Question 56:

If points A (5, p) B (1, 5), C (2, 1) and D (6, 2) form a square ABCD, then p =

(a) 7

(b) 3

(c) 6

(d) 8

Answer:

The distance d between two points and is given by the formula

In a square all the sides are equal to each other.

Here the four points are A(5,p), B(1,5), C(2,1) and D(6,2).

The vertex ‘A’ should be equidistant from ‘B’ as well as D’

Let us now find out the distances ‘AB’ and ‘AD’.

These two need to be equal.

Equating the above two equations we have,

Squaring on both sides we have,

Hence the correct choice is option (c).

Page No 98:

Question 57:

The coordinates of the circumcentre of the triangle formed by the points O (0, 0), A (a, 0 and B (0, b) are

(a) (a, b)

(b) a2,b2

(c) b2, a2

(d) (b, a)

Answer:

The distance d between two points and is given by the formula

The circumcentre of a triangle is the point which is equidistant from each of the three vertices of the triangle.

Here the three vertices of the triangle are given to be O(0,0), A(a,0) and B(0,b).

Let the circumcentre of the triangle be represented by the point R(x, y).

So we have

Equating the first pair of these equations we have,

Squaring on both sides of the equation we have,

Equating another pair of the equations we have,

Squaring on both sides of the equation we have,

Hence the correct choice is option (b).

Page No 98:

Question 58:

The coordinates of a point on x-axis which lies on the perpendicular bisector of the line segment joining the points (7, 6) and (−3, 4) are

(a) (0, 2)

(b) (3, 0)

(c) (0, 3)

(d) (2, 0)

Answer:

TO FIND: The coordinates of a point on x axis which lies on perpendicular bisector of line segment joining points (7, 6) and (−3, 4).

Let P(x, y) be any point on the perpendicular bisector of AB. Then,

PA=PB

On x-axis y is 0, so substituting y=0 we get x= 3

Hence the coordinates of point is i.e. option (b) is correct

Page No 98:

Question 59:

The length of a line segment joining A (2, −3) and B is 10 units. If the abscissa of B is 10 units, then its ordinates can be

(a) 3 or −9

(b) −3 or 9

(c) 6 or 27

(d) −6 or −27

Answer:

It is given that distance between P (2,−3) and is 10.

In general, the distance between A and B is given by,

So,

On further simplification,

We will neglect the negative value. So,

So the answer is (a)

Page No 98:

Question 60:

If the line segment joining the points (3, –4), and (1, 2) is trisected at points P(a, –2) and Q53, b. Then,

(a) a=83, b=23

(b) a=73, b=0

(c) a=13, b=1

(d) a=23, b=13

Answer:

Given that, the line segment formed by joining the points A(3, –4), and B(1, 2) is trisected at points P(a, –2) and Q53, b.

Using the section formula, the coordinates of the point O(xy) which divides the line segment joining the points X(x1y1) and Y(x2y2), internally, in the ratio m1 : m2 are given by m1x2+m2x1m1+m2,m1y2+m2y1m1+m2.

Now, point P divides AB in the ratio 1 : 2.
Thus,
a,-2=11+231+2,12+2-41+2=73,-2
a=73

While point divides AB in the ratio 2 : 1.
Thus,
53,b=21+132+1,22+1-42+1=53,0
b=0

Hence, the correct answer is option (b).
 

Page No 98:

Question 61:

The given figure shows the plans for a sun room. It will be built onto the wall of a house. The four walls of the sun room are square clear glass panels. The roof is made of four trapezium shape clear glass panels of same size and one tinted glass panel in half a regular octagon shape.



(i) In the top view, find the mid-point of the segment joining the point J(6, 17) and I(9, 16).
 

(a) 332, 152

(b) 32, 12

(c) 152,332

(d) 12,32

(ii) In the top view, the distance of the point P from the y-axis is
(a) 5
(b) 15
(c) 19
(d) 25

(iii) In the front view, the distance between the point A and S is
(a) 4
(b) 8
(c) 16
(d) 20

(iv) In the front view, find the co-ordinates of the point which divides the line segment joining the points A and B in the ratio 1 : 3 internally.
(a) (8.5, 2.0)
(b) (2.0, 9.5)
(c) (3.0, 7.5)
(d) (2.0, 8.5)

(v) In the front view, if a point (x, y) is equidistant from the Q(9, 8) and S(17, 8), then
(a) x + y = 13
(b) x – 13 = 0
(c) y – 13 = 0
(d) xy = 13

Answer:

(i) The mid-point of a line segment joining the points Ax1,y1 and Bx2,y2 is given by the coordinates x1+x22,y1+y22.
Here, a line segment is formed by joining the point J(6, 17) and I(9, 16).
Thus,
Coordinates of mid-point of IJ=6+92,17+162=152,332

Hence, the correct answer is option (c).

(ii) In the front view, we see that point P is 5 cm away from the y-axis and has coordinates (5, 8). Since the scale is given as 1 cm = 1 m, the distance of point P from the y-axis is 5 m.

Hence, the correct answer is option (a).

Disclaimer: Refer to the front view for point P and not the top view.

(iii) In the front view, the coordinates of point A are (1, 8) and that of point S are (17, 8).
Thus, the distance between the two points on the graph A and S is 17 − 1 = 16 cm. That means that the distance between the two points is actually 16 m.

Hence, the correct answer is option (c).

(iv) Given that, the line segment joining the points A and B in the ratio 1 : 3 internally. Now, the coordinates of point A are (1, 8) and that of point B are (5, 10). Let the point that divides AB in ratio 1 : 3 be M.
Thus,
Coordinates of M=m1x2+m2x1m1+m2,m1y2+m2y1m1+m2=1×5+3×11+3,1×10+3×81+3=84,344=2.0,8.5

Hence, the correct answer is option (d).

(v) Given that, a point (xy) is equidistant from the Q(9, 8) and S(17, 8). Let the point be N(xy).
Thus, NQ = SN.
x-92+y-82=17-x2+8-y2x2+81-18x+y2+64-16y=289+x2-34x+64+y2-16y81-18x=289-34x34x-18x=289-8116x=208x=13x-13=0

Hence, the correct answer is option (b).



Page No 99:

Question 62:

Class X students of a secondary school in Krish Nagar have been allotted a rectangular plot of land for gardening activity. Saplings of Gulmohar are planted on the boundary at a distance of 1 m from each other. There is a triangular grassy lawn in the plot as shown in the given figure. The students are to sow seeds of flowering plants on the remaining area of the plot. Considering A as origin, AD along x-axis and AB along y-axis answer questions:



(i) What are the coordinates of A?

(a) (0, 1)
(b) (1, 0)
(c) (0, 0)
(d) (–1, –1)

(ii) What are the coordinates of P?
(a) (4, 6)
(b) (6, 4)
(c) (4, 5)
(d) (5, 4)

(iii) What are the coordinates of R?
(a) (6, 5)
(b) (5, 6)
(c) (6, 0)
(d) (7, 4)

(iv) What are the coordinates of D?
(a) (16, 0)
(b) (0, 0)
(c) (0, 16)
(d) (16, 1)

(v) What are the coordinates of P, if D is taken as the origin, DA along negative x-axis and DC along y-axis?
(a) (12, 2)
(b) (–12, 6)
(c) (12, 3)
(d) (6, 10)

Answer:

(i) According to the given figure, point A is taken as the origin. Therefore, the coordinates of point A are (0, 0).

Hence, the correct answer is option (c).

(ii) According to the given figure, the abscissa for point P is 4 and its ordinate is 6. Therefore, the coordinates of point P are (4, 6).

Hence, the correct answer is option (a).

(iii) According to the given figure, the abscissa for point R is 6 and its ordinate is 5. Therefore, the coordinates of point R are (6, 5).

Hence, the correct answer is option (a).

(iv) According to the given figure, the abscissa for point D is 16 and its ordinate is 0 as it lies on the x-axis. Therefore, the coordinates of point D are (16, 0).

Hence, the correct answer is option (a).

(v) Given that, D is taken as the origin, DA along negative x-axis and DC along y-axis. Now, point P lies 12 units away from D towards the negative x-axis and 6 units away on the positive y-axis. Thus, the coordinates of P is (−12, 6).

Hence, the correct answer is option (b).

Page No 99:

Question 63:

Four persons John, Saurabh, Salim and Ratan are sitting in a courtyard at points A, B, C and D respectively as shown in the given figure. The Courtyard has been divided into small squares by drawing equality spaced horizontal and vertical lines. Taking OX and OY as the coordinate axes, answer the following questions:
 


(i) The coordinates of points A are

(a) (4, 3)
(b) (3, 4)
(c) (3, 3)
(d) (4, 4)

(ii) By joining A to B, B to C, C to D and D to A, the figure formed is not a
(a) rhombus
(b) square
(c) parallelogram
(d) trapezium

(iii) The distance between the mid-points of AC and BD is
(a) 2
(b) 3
(c) 0
(d) 1

(iv) Area of ∆ABC is
(a) 18 sq. units
(b) 9 sq. units
(c) 12 sq. units
(d) 16 sq. units

(v) Perimeter of quadrilateral ABCD is
(a) 413
(b) 313
(c) 213
(d) 13

Answer:

(i) According to the given figure, the abscissa is 3 and ordinate is 4. Thus, the coordinates of point A are (3, 4).

Hence, the correct answer is option (b).

(ii) From the figure, we get the points as A(3, 4), B(6, 7), C(9, 4) and D(7, 2).
The distance between two points x1,y1 and x2,y2 is given as d=x2-x12+y2-y12.

Here,
AB=6-32+7-42=9+9=18=32 units
BC=9-62+4-72=9+9=18=32 units
CD=7-92+2-42=4+4=8=22 units
DA=7-32+2-42=16+4=20=25 units
Since opposite pair of sides of the quadrilateral formed are not equal, the figure is not a parallelogram. Since it is not a parallelogram, it cannot be a square or a rhombus.

Hence, the correct options are option (a), (b) and (c).

Disclaimer: The figure formed is not a parallelogram as per the above solution. Since it is not a parallelogram, it cannot be a square or a rhombus. Thus, the figure formed is a trapezium.

(iii) The coordinates of the mid-point of a line segment with coordinates of the endpoints as x1,y1 and x2,y2 are given as x1+x22,y1+y22.

Now,
Coordinates of mid-point of AC=3+92,4+42=122,82=6,4

Coordinates of mid-point of BD=6+72,7+22=132,92

Using the distance formula to find the distance between the two points,
d=x2-x12+y2-y12=6-1322+4-922=-122+-122=12 units



Page No 100:

Question 64:

A City school is organizing annual sports event in a rectangular shaped ground ABCD. The tracks are being marked with a gap of 1 m each in the form of straight lines. 120 flower pots are placed with a distance of 1 m each along AD. Shruti runs 13rdof the distance in the second line along AD and post her flag. Saanvi runs 15th of the distance AD in the eighth line and posts her flag.



(i) The distance between the two flags is
(a) 273
(b) 373
(c) 273
(b) 73

(ii) If Reena has to post the flags exactly halfway between the line segment joining the two flags, the coordinates where she should post her flag are
(a) (2, 40)
(b) (2, 30)
(c) (5, 32)
(d) (10, 64)

(iii) The coordinates where Shruti posts her flag are
(a) (2, 40)
(b) (40, 2)
(c) (2, 30)
(d) (3, 40)

(iv) The coordinates where Saanvi posts her flag are
(a) (3, 40)
(b) (24, 8)
(c) (5, 32)
(d) (8, 24)

Answer:

(i) Shruti runs 13rdof the distance in the second line along AD and post her flag. Saanvi runs 15th of the distance AD in the eighth line and posts her flag. Thus, Shruti runs 40 m while Saanvi runs 24 m. Therefore, the coordinates of Shruti's flag is (2, 40) and that of Saanvi's flag is (8, 24).

The distance between two points x1,y1 and x2,y2 is given as d=x2-x12+y2-y12.

Thus, distance between the two flags is given as:
d=8-22+24-402=36+256=292 m=273 m

Hence, the correct answer is option (a).

(ii) Reena's flag is exactly halfway between the line segment joining the two flags.
The coordinates of the mid-point of a line segment with coordinates of the endpoints as x1,y1 and x2,y2 are given as x1+x22,y1+y22.

Thus,
Coordinates of Reena's flag=x1+x22,y1+y22=2+82,40+242=102,642=5,32

Hence, the correct answer is option (c).

(iii) Shruti runs 13rdof the distance, i.e., 40 m in the second line along AD and post her flag. Therefore, the coordinates of Shruti's flag is (2, 40).

Hence, the correct answer is option (a).

(iv)  Saanvi runs 15th of the distance AD, i.e., 24 min the eighth line and posts her flag. Therefore, the coordinates of Saanvi's flag is (8, 24).

Hence, the correct answer is option (d).



Page No 101:

Question 65:

Each of the following questions contains STATEMENT-1 (Assertion) and STATEMENT-2 (Reason) and has following four choices (a), (b), (c) and (d), only one of which is the correct answer. Mark the correct choice.
(a) Statement-1 is true, Statement-2 is true; Statement-2 is a correct explanation for Statement-1.
(b) Statement-1 is true, Statement-2 is true; Statement-2 is not a correct explanation for Statement-1.
(c) Statement-1 is true, Statement-2 is false.
(d) Statement-1 is false, Statement-2 is true.
Statement-1 (Assertion): If a + b + c = 0, then the centroid of the triangle whose vertices are P(a, b), Q(b, c) and R(c, a) is at the origin.

Statement-2 (Reason): The coordinates of the centroid of the triangle whose vertices are A(x1, y1), B(x2, y2) and C(x3, y3) are x1+x2+x33, y1+y2+y33.
 
 

Answer:

Statement-1 (Assertion): If a + b + c = 0, then the centroid of the triangle whose vertices are P(ab), Q(bc) and R(ca) is at the origin.


The coordinates of the centroid of the triangle whose vertices are A(x1y1), B(x2y2) and C(x3y3) are x1+x2+x33, y1+y2+y33. Now, let the vertices of PQR be P(ab), Q(bc) and R(ca).
Thus, 
Coordinates of its centroid=a+b+c3, b+c+a3=03, 03                    a+b+c=0=0,0
So, its centroid is at the origin. Thus, Statement-1 is true.

Statement-2 (Reason): The coordinates of the centroid of the triangle whose vertices are A(x1y1), B(x2y2) and C(x3y3) are x1+x2+x33, y1+y2+y33.

Let the vertices of ABC be A(x1y1), B(x2y2) and C(x3y3). Let AD be the median of the ABC drawn from point A and D is the mid-point of BC. Now, the coordinates of the mid-point of a line segment with coordinates of the endpoints as x1,y1 and x2,y2 are given as x1+x22,y1+y22.

Thus, coordinates of D=x2+x32,y2+y32.

Now, let G be the centroid of the ABC that divides the median AD in the ratio 2 : 1.
Coordinates of G=m1x2+m2x1m1+m2,m1y2+m2y1m1+m2=2×x2+x32+1×x12+1,2×y2+y32+1×y12+1=x1+x2+x33, y1+y2+y33

Thus, Statement-2 is also true and is the correct explanation of Statement-1.

Hence, the correct answer is option (a).

Page No 101:

Question 66:

Each of the following questions contains STATEMENT-1 (Assertion) and STATEMENT-2 (Reason) and has following four choices (a), (b), (c) and (d), only one of which is the correct answer. Mark the correct choice.
(a) Statement-1 is true, Statement-2 is true; Statement-2 is a correct explanation for Statement-1.
(b) Statement-1 is true, Statement-2 is true; Statement-2 is not a correct explanation for Statement-1.
(c) Statement-1 is true, Statement-2 is false.
(d) Statement-1 is false, Statement-2 is true.
Statement-1 (Assertion): If origin is the centroid of triangle whose vertices are P(a, b), Q(b, c) and R(c, a), then a3 + b3 + c3 = 3abc.
Statement-2 (Reason): If a + b + c = 0, then a3 + b3 + c3 = 3abc.

Answer:

Statement-1 (Assertion): If origin is the centroid of triangle whose vertices are P(ab), Q(bc) and R(ca), then a3 + b3 + c3 = 3abc.

The coordinates of the centroid of the triangle whose vertices are A(x1y1), B(x2y2) and C(x3y3) are x1+x2+x33, y1+y2+y33.
Now, let the vertices of PQR be P(ab), Q(bc) and R(ca) and its centroid be (0, 0).
So,
Coordinates of its centroid=a+b+c3, b+c+a30,0=a+b+c3, b+c+a3a+b+c=0

Now,
a+b+c3=a3+b3+c3+3a+bb+cc+aa3+b3+c3=0-3-c-a-b                 a+b+c=0a3+b3+c3=3abc

Thus, Statement-1 is true.

Statement-2 (Reason): If a + b + c = 0, then a3 + b3 + c3 = 3abc.

We know that a+b+c3=a3+b3+c3+3a+bb+cc+a.
Thus,
a+b+c3=a3+b3+c3+3a+bb+cc+aa3+b3+c3=0-3-c-a-b                 a+b+c=0a3+b3+c3=3abc

Thus, Statement-2 is true and is the correct explanation of Statement-1.

Hence, the correct answer is option (a).
 

Page No 101:

Question 67:

Each of the following questions contains STATEMENT-1 (Assertion) and STATEMENT-2 (Reason) and has following four choices (a), (b), (c) and (d), only one of which is the correct answer. Mark the correct choice.
(a) Statement-1 is true, Statement-2 is true; Statement-2 is a correct explanation for Statement-1.
(b) Statement-1 is true, Statement-2 is true; Statement-2 is not a correct explanation for Statement-1.
(c) Statement-1 is true, Statement-2 is false.
(d) Statement-1 is false, Statement-2 is true.
Statement-1 (Assertion): If the coordinates of the mid-points of sides AB and AC of ∆ABC are D(3, 5), and E(–3, –3) respectively, then BC = 20 units.
Statement-2 (Reason): The line segment joining the mid-points of two sides of a triangle is parallel to the third side.

Answer:

Statement-1 (Assertion): If the coordinates of the mid-points of sides AB and AC of ∆ABC are D(3, 5), and E(–3, –3) respectively, then BC = 20 units.

Consider a ABC with mid-points of sides AB and AC of ∆ABC are D(3, 5), and E(–3, –3) respectively. Let the vertices of be Ax1,y1, Bx2,y2 and Cx3,y3.

Statement-2 (Reason): The line segment joining the mid-points of two sides of a triangle is parallel to the third side.

Page No 101:

Question 68:

Each of the following questions contains STATEMENT-1 (Assertion) and STATEMENT-2 (Reason) and has following four choices (a), (b), (c) and (d), only one of which is the correct answer. Mark the correct choice.
(a) Statement-1 is true, Statement-2 is true; Statement-2 is a correct explanation for Statement-1.
(b) Statement-1 is true, Statement-2 is true; Statement-2 is not a correct explanation for Statement-1.
(c) Statement-1 is true, Statement-2 is false.
(d) Statement-1 is false, Statement-2 is true.
Statement-1 (Assertion): A triangle with vertices at (4, 0), (–1, –1), and (3, 5) is isosceles right angled triangle.
Statement-2 (Reason): If ABC is an isosceles triangle, then it is right angled.

Answer:

Statement-1 (Assertion): A triangle with vertices at (4, 0), (–1, –1), and (3, 5) is isosceles right angled triangle.

Consider the vertices of ABC as A(4, 0), B(–1, –1) and C(3, 5). Now, the distance between two points x1,y1 and x2,y2 is given as d=x2-x12+y2-y12.

Thus,
AB=-1-42+-1-02=25+1=26 units

BC=3+12+5+12=16+36=52 units=213 units

CA=4-32+0-52=1+25=26 units

Thus, AB = CA ≠ BC.

Applying Pythagoras theorem in ABC,
AB2+CA2=262+262=26+26=52=AB2
AB2+CA2=AB2

Therefore, ABC is an isosceles right angled triangle. Thus, Statement-1 is true.

Statement-2 (Reason): If ABC is an isosceles triangle, then it is right angled.

Consider the vertices of ABC as A(3, 2), B(0, 0) and C(2, 3). Now, the distance between two points x1,y1 and x2,y2 is given as d=x2-x12+y2-y12.

Thus,
AB=0-32+0-22=9+4=13 units

BC=2-02+3-02=4+9=13 units

CA=2-32+3-22=1+1=2 units

Therefore, ABC is an isosceles triangle.

Applying Pythagoras theorem in ABC,
AB2+BC2=132+132=13+13=26AB2
AB2+CA2AB2

Therefore, ABC is an isosceles triangle but not right-angled. Thus, Statement-2 is false.

Hence, the correct answer is option (c).

Page No 101:

Question 69:

Each of the following questions contains STATEMENT-1 (Assertion) and STATEMENT-2 (Reason) and has following four choices (a), (b), (c) and (d), only one of which is the correct answer. Mark the correct choice.
(a) Statement-1 is true, Statement-2 is true; Statement-2 is a correct explanation for Statement-1.
(b) Statement-1 is true, Statement-2 is true; Statement-2 is not a correct explanation for Statement-1.
(c) Statement-1 is true, Statement-2 is false.
(d) Statement-1 is false, Statement-2 is true.
Statement-1 (Assertion): If a ≠ 0, b ≠ 0, then the points O(0, 0), A(a, a2), B(b, b2) are non-collinear.
Statement-2 (Reason): If points P, Q and R are collinear, then PQ + QR = PR.

Answer:

Statement-1 (Assertion): If a ≠ 0, b ≠ 0, then the points O(0, 0), A(aa2), B(bb2) are non-collinear.

Consider three points O(0, 0), A(aa2) and B(bb2) as the vertices of OAB. If these points are non-collinear, then OA + OB ≠ AB. The distance between two points x1,y1 and x2,y2 is given as d=x2-x12+y2-y12.
Here,
OA=0-a2+0-a22=a2+a4=a1+a2

OB=0-b2+0-b22=b2+b4=b1+b2

AB=a-b2+a2-b22=a-b21+a+b2=a-b1+a+b2

OA+OB=a1+a2+b1+b2a-b1+a+b2OA+OBAB

Therefore, the points O(0, 0), A(aa2), B(bb2) are non-collinear. Thus, Statement-1 is true.

Statement-2 (Reason): If points P, Q and R are collinear, then PQ + QR = PR.

Three points are collinear if they lie on the same line. It is given that the points P, Q and R are collinear. Thus, they lie on the same line.
If point Q lies between the points P and R, then PQ + QR = PR.

Thus, Statement-2 is true and is the correct explanation of Statement-1.

Hence, the correct answer is option (a).



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