# Co Ordinate Geometry - Problems and Solutions

1.

In which quadrant does the point(-4, -7) lie?

A.) 1st
B.) 2nd
C.) 3rd
D.) 4th

Answer: Option 'C'

The point (-4, -7) lies in 3rd quadrant.

2.

In which quadrant does the point(1, 5) lie?

A.) 1st
B.) 2nd
C.) 3rd
D.) 4th

Answer: Option 'A'

The point (1, 5) lies in 1st quadrant.

3.

In which quadrant does the point(9, -2) lie?

A.) 1st
B.) 2nd
C.) 3rd
D.) 4th

Answer: Option 'D'

The point (9, -2) lies in 4th quadrant.

4.

In which quadrant does the point(-7, 6) lie?

A.) 1st
B.) 2nd
C.) 3rd
D.) 4th

Answer: Option 'B'

The point (-7, 6) lies in 2nd quadrant.

5.

In which quadrant does the point(0, 9) lie?

A.) x-axis
B.) y-axis
C.) 3rd
D.) None of these

Answer: Option 'B'

Answer: Option 'B'
The point (0, 9) lies in x-axis.

6.

In which quadrant does the point(9, 0) lie?

A.) x-axis
B.) y-axis
C.) 4th
D.) None of these

Answer: Option 'A'

The point (9, 0) lies in y-axis.

7.

Find the distance of the point A(4, -4) from the origin.

A.) 3√2
B.) 2√8
C.) 6√2
D.) 8√2

Answer: Option 'D'

OA = √42+(-4)2 = √16+16 = √32 = 8√2

8.

Find the distance of the point A(3, -3) from the origin.

A.) 3√2
B.) 3√6
C.) 6√2
D.) 7√2

Answer: Option 'A'

OA = √32+(-3)2 = √9+9 = √18 = 3√2

9.

P is a point on x-axis at a distance of 4 units from y-axis to its right. The co-ordinates of P are:

A.) (4, 0)
B.) (0, 4)
C.) (4, 4)
D.) (-4, 4)

Answer: Option 'A'

The co-ordinates of P are A(4, 0)

10.

A is a point on y-axis at a distance of 5 units from x-axis lying below x-axis. The co-ordinates of A are:

A.) (5, 0)
B.) (-5, 0)
C.) (0, 5)
D.) (0, -5)

Answer: Option 'D'

The co-ordinates of A are A(0, -5)

11.

Find the distance of the point A(4, -2) from the origin.

A.) 4√5 units
B.) 2√5 units
C.) 5√2 units
D.) 7√2 units

Answer: Option 'B'

OA = √4 - 02+(-2 - 0)2 = √16+4 = √20 = √4 × 5 = 2√5 units

12.

Find the distance between the points A(-4, 7) and B(2, -5).

A.) 8√5 Units
B.) 6√5 Units
C.) 6√4 Units
D.) None of these

Answer: Option 'B'

AB = √(2+4)2 + (-5-7)2
= √62 + (-12)2
= √36+144 = √180
=√36 × 5 = 6√5 units.

13.

The distance between the points A(b, 0) and B(0, a) is.

A.) √a2-b2.
B.) √a2+b2.
C.) √a+b
D.) a-b

Answer: Option 'B'

AB = √(b-0)2-(0-a)2
= √b2+a2
= √a2+b2.

14.

If the distance of the point P(x, y) from A(a, 0) is a + x, then y2 = ?

A.) 8ax
B.) 6ax
C.) 4ax
D.) 2ax

Answer: Option 'C'

√(x-a)2+(y-0)2 = a + x
= (x-a)2+y2
= (a+x)2 => y2 = (x-a)2-(x-a)2-4ax => y2 = 4ax

15.

The distance between the points A(5, -7) and B(2, 3) is:

A.) 109
B.) 5√7
C.) √109
D.) None of these

Answer: Option ''

AB2 = (2 - 5)2 + (3 + 7)2
=> (-3)2 + (10)2
=> 9 + 100 => √109

16.

Find the area of ΔABC whose vertices are A(9, -5), B(3, 7) and (-2, 4).

A.) 29 units
B.) 35.9 sq.units
C.) 39 sq.units
D.) 39.5 sq.units

Answer: Option 'C'

Here, x1 = 9, x2 = 3, x3 = -2 and y1 = -5, y2 = 7, y3 = 4
= 1/2 [9(7-4) + 3(4+5) + (-2)(-5-7)]
= 1/2 [9(3) + 3(9) - 2(-12)]
= 1/2 [27 + 27 + 24]
= 1/2 [78]
= 39 sq.units

17.

Find the area of ΔABC whose vertices are A(2, -5), B(4, 9) and (6, -1).

A.) 9 units
B.) 5 sq.units
C.) 7 sq.units
D.) 6 sq.units

Answer: Option 'D'

Here, x1 = 2, x2 = 4, x3 = 6 and y1 = -5, y2 = 9, y3 = -1
= 1/2 [2(9+1) + 4(-1+5) + 6(5-9)]
= 1/2 [2(10) + 4(4) + 6(-4)]
= 1/2 [20 + 16 - 24]
= 1/2 [12]
= 6 sq.units

18.

The points A(0, 6), B(-5, 3) and C(3, 1) are the vertices of a triangle which is ?

A.) equilateral
B.) right angled
C.) isosceles
D.) scalene

Answer: Option 'C'

AB2= (-5 - 0)2 + (-3 - 0)2 = 16 + 9 = 25
BC2 = (3 + 5)2 + (1-3)2 = 82 + (-2)2 = 64 + 4 = 68
AC2 = (3 - 0)2 + (1 - 6)2 = 9 + 25 = 34.
AB = AC. ==> ΔABC is isosceles.

19.

The points A(-4, 0), B(1, -4), and C(5, 1) are the vertices of

A.) An isosceles right angled triangle
B.) An equilateraltriangle
C.) A scalene triangle
D.) None of these

Answer: Option 'A'

AB2 = (1 + 4)2 + (-4 - 0)2
= 25 + 16 = 41,
BC2 = (5 - 1)2 + (1 + 4)2 = 42 + 52
= 16 + 25 = 41
AC2 = (5 + 4)2 + (1 - 0)2
= 81 + 1 = 82
AB = BC and AB2 = BC2 = AC2
ΔABC is an isosceles right angled triangle

20.

Find the vertices of triangle are A(2, 8), B(-4, 3) and (5, -1). The area of ΔABC is:

A.) 5 1/2 sq.units
B.) 2 1/3 sq.units
C.) 2 1/2 sq.units
D.) None of these

Answer: Option 'C'

Here, x1 = 2, x2 = -4, x3 = 5 and y1 = 8, y2 = 2, y3 = -1
= 1/2 [2(3+1) - 4(-1-8) + 5(8-3)]
= 1/2 [2(4) + 4(-9) + 5(5)]
= 1/2 [16 - 36 + 25]
= 1/2 [5]
= 2 1/2 sq.units

21.

Find the value of k for which the points A(-2, 5), B(3, k) and C(6, 1) are collinear.

A.) 5
B.) 4
C.) 7
D.) 1

Answer: Option 'D'

x>1 = -2, x>2 = 3, x>3 = 6 and y>1 = 5, y>2 = k, y>3 = -1
Now Δ = 0 <=> -2(k + 1) + 3(-1 + 5) + 6(5 - k) = 0
<=> -2 (k+1) + 3(4) + 6(5-k) = 0
<=> -2k-2 + 12+30 -6k = 0
<=> 40 - 8k = 0
<=> -8k = -40
<=> k = 5.

22.

Find the value of k for which the points A(-2, 6), B(5, k) and C(8, 3) are collinear.

A.) 5
B.) 4
C.) 7
D.) 1

Answer: Option 'A'

x1 = -2, x2 = 5, x3 = 8 and y1 = 6, y2 = k, y3 = 3
Now Δ = 0 <=> -2(k - 3) + 5(3 - 6) + 8(6 - k) = 0
<=> -2 (k-3) + 5(-3) + 8(6-k) = 0
<=> -2k + 6 - 15 + 48 - 8k = 0
<=> 39 - 10k = 0
<=> k = -(39/10)
<=> k = 3.9.

23.

If the A(2, 3), B(5, k), and C(6, 7) are collinear, then k = ?

A.) 11
B.) 12
C.) 18
D.) 6

Answer: Option 'D'

x1 = 2, x2 = 5, x3 = 6 and y1 = 3, y2 = k, y3 = 7
Now Δ = 0 <=> 2(k - 7) + 5(7 - 3) + 6(3 - k) = 0
<=> 1/2 [2 (k-7) + 5(4) + 6(3-k)] = 0
<=> 2k - 14 + 20 + 18 - 6k = 0
<=> 24 - 4k = 0
<=> 4k = 24
<=> k = 6.

24.

If the points A(1, 2), B(2, 4), and C(k, 6) are collinear, then k = ?

A.) 3
B.) -3
C.) 4
D.) -4

Answer: Option 'B'

x1 = 1, x2 = 2, x3 = k and y1 = 2, y2 = 4, y3 = 6
= 1(4 - 6) + 2 (6 - 2) + k(2 - 4)
= -2 + 12 - 4 + 2k - 4k = 0
= 6 - 2k = 0
= -2k = 6
= k = -3.

25.

Find the co-ordinates of the centroid of ΔABC whose vertices are A(7, -3), B(5, -4) and C(-3, -5)?

A.) 3, -3
B.) 3, -4
C.) 4, -3
D.) None of these

Answer: Option 'B'

x1 = 7, x2 = 5, x3 = -3 and y1 = -3, y2 = -4, y3 = -5
= [(7 + 5 - 3)/3, (-3 - 4 - 5)/3]
= (12-3)/3, -12/3)
= (9/3, -12/3)
= (3, -4)

26.

The co-ordinates of the end points of a diameter AB of a circle are A(-6, 8) and B(-10, 6). Find the  co-ordinates of its centre.

A.) -8, 7
B.) -7, 8
C.) 7, -8
D.) -8, -7

Answer: Option 'A'

The center O is the mid point of AB.
Co-ordinates of O are [(-6-10)/2, (8+6)/2]
= -16/2, 14/2
= (-8, 7)

27.

Find the co-ordinates of a point P which divides the join of A(5, -4) and B(10, 8) in the ratio 3 : 2.

A.) 9, 5
B.) 7, 8
C.) 8, 7
D.) 9, -7

Answer: Option 'C'

Required point is P = (mx2 + nx1)/m+n, (my2 + ny1)/m+n
P((3(10) + 2(5))/5, (3(15) + 2(-5))/5)
=(30 + 10)/5, (45-10)/5
= P(8, 7)

28.

A point C divides the join of A(2,5) and B(3,9) in the ratio 3 : 4. The co-ordinates of C are:

A.) (15/7, 46/7)
B.) (15/7, 47/7)
C.) (15/7, 40/7)
D.) None of these

Answer: Option 'B'

x1=2, x2=3 and y1=3, y2=7
= [(3 × 3 + 4 × 2)/7, (3 × 9 + 4 × 5)/7]
= 9+6/7, 27+20/7
= (15/7, 47/7)

29.

The end points of a line segment AB are A(-6, 4) and B(12,24). Its midpoint is:

A.) (14, 4)
B.) (-4, 14)
C.) (3, 14)
D.) (-3, 14)

Answer: Option 'D'

Midpoint is C((-6+12)/2, (4+24)/2)
(-6/2, 28/2) = (-3, 14)

30.

The vertices of a ΔABC are A(-6, 18), B(12, 0) and C(9, −21). The centroid of ΔABC is:

A.) (5, 1)
B.) (5, -1)
C.) (4, -1)
D.) None of these

Answer: Option 'B'

CENTROID OF A TRIANGLE
The point of intersection of all the medians of a triangle is called its centroid.
If A(x1, y1), B(x2, y2) and C(x3, y3) be the vertices of ΔABC,
then the co-ordinates of its centroid are [1/3(x1 + x2 + x3), 1/3(y1 + y2 + y3)]
= [1/3(-6+12+9), 1/3(18+0-21)]
= [15/3, -3/3]
= (5, -1)

31.

The vertices of a quadrilateral ABCD are A(0, 0), B(3,3), C(3, 6) and D(0, 3). Then , ABCD is a

A.) square
B.) parallelogram
C.) rectangle
D.) rhombus

Answer: Option 'B'

AB2 = (3-0)2 + (3-0)2 = 18
BC2 = (3-3)2 + (6-3)2 = 9
CD2 = (0-3)2 + (3-6)2 =18
AD2 = (0-0)2 + (3-0)2 = 9
AB = CD = √18 => 3√2,
BC = AD = √9
AC2 = (3-0)2 + (6-0)2 = 9 + 36 = 45
BD2 = (0-3)2 + (3-3)2 = 9 + 0 = 9
AC ≠ BD
ABCD is a parallelogram.

32.

The points A(1, -3), B(13, 9), C(10, 12) and D(-2, 0) taken in order are the vertices of

A.) square
B.) rhombus
C.) parallelogram
D.) rectangle

Answer: Option 'D'

AB2 = (13-1)2 + (9+3)2
= 122 + 122 = 288.
BC2 = (10-13)2 + (12-9)2
= -32 + 32 = 9+9 = 18
CD2 = (10+2)2 + (12-0)2
= 122 + 122 = 288
AD2 = (-2-1)2 + (0+3)2 = (9+9) =18
AB = CD and BC = AD
AC2 = (10-1)2 + (12+3)2
= 92 + 152 = 81 + 225 = 306.
BD2 = (-2-13)2 + (0-9)2
= 225 + 81 = 306
AC = BD
ABCD is a rectangle.

33.

If for a line m = tanϑ < 0, then

A.) ϑ is acute
B.) ϑ is obtuse
C.) ϑ = 90°
D.) ϑ = 60°

Answer: Option 'B'

m = tanϑ < 0 => is obtuse

34.

If for a line m = tanϑ > 0, then

A.) ϑ is acute
B.) ϑ is obtuse
C.) ϑ = 90°
D.) ϑ = 60°

Answer: Option 'A'

m = tanϑ < 0 => is acute