1. Find the area of the triangle whose vertices are A(2,4), B(−3,7) and C(−4,5).
A(2,4), B(−3,7) āĻā§°ā§ C(−4,5) āĻŦāĻŋāύā§āĻĻā§ā§°ā§ āĻāĻ āĻŋāϤ āϤā§ā§°āĻŋāĻā§āĻā§° āĻā§āώā§āϤā§ā§°āĻĢāϞ āĻāĻŋāĻŽāĻžāύ?
Options:
Options: (a) 11 sq units (b) 22 sq units (c) 7 sq units (d) 6.5 sq units
Ans: (d) 6.5 sq units
Soln
Area = 1â/2 âŖx1â(y2â-y3â) + x2â(y3â-y1â) + x3â(y1â- y2â)
=1â/2[2(7-5) + (-3)(5-4)+(−4)(4−7)]
=1/2[4−3+12]
=1/2â(13)
= 6.5
2.Find the area of the triangle whose vertices are A(10,−6), B(2,5) and C(−1,3).
A(10,−6), B(2,5) āĻā§°ā§ C(−1,3) āĻŦāĻŋāύā§āĻĻā§ā§°ā§ āĻāĻ āĻŋāϤ āϤā§ā§°āĻŋāĻā§āĻā§° āĻā§āώā§āϤā§ā§°āĻĢāϞ āĻāĻŋāĻŽāĻžāύ?
Options: (a) 12.5 (b) 24.5 (c) 7 (d) 6.5
Ans: (b) 24.5 sq units
Soln
= 1â/2 [10(5−3)+2(3+6)+(−1)(−6−5)]
=1â/2 [20+18+11]
= 24.5
3. Find the area of the triangle whose vertices are A(4,4), B(3,−16) and C(3,−2).
A(4,4), B(3,−16) āĻā§°ā§ C(3,−2) āĻŦāĻŋāύā§āĻĻā§ā§°ā§ āĻāĻ āĻŋāϤ āϤā§ā§°āĻŋāĻā§āĻā§° āĻā§āώā§āϤā§ā§°āĻĢāϞ āĻāĻŋāĻŽāĻžāύ ?
Options:
Options: (a) 12.5 (b) 24.5 (c) 7 (d) 6.5
Ans: (c) 7 sq units
Soln
Points B and C have same x-coordinate → vertical line.
Base = |−16 − (−2)| = 14
Height = |4 − 3| = 1
Area = 1/2 × 14 × 1 = 7
4. For what value of x are the points A(−3, 12), B(7, 6) and C(x, 9) collinear ?
Options: (a) 1 (b) −1 (c) 2 (d) −2
Ans: (c) 2
Soln
Slope AB = −3/5, Slope AC = −3/(x+3)
3â/5 = - 3/x+3
⇒ x + 3 = 5
⇒ x = 2â
5. For what value of y are the points A(1,4), B(3,y) and C(−3,16) collinear ?
A(1,4), B(3,y) āĻā§°ā§ C(−3,16) āĻŦāĻŋāύā§āĻĻā§āĻŦā§ā§° āĻāĻā§ āϏāϰāϞ⧰ā§āĻāĻžāϤ āĻĨāĻžāĻāĻŋāĻŦāϞ⧠y ā§° āĻŽāĻžāύ āĻāĻŋāĻŽāĻžāύ ?
Options: (a) 1 (b) −1 (c) 2 (d) −2
Ans: (d) −2
Soln
Slope AC = −3, Slope AB = (y−4)/2
y - 4â/2 = −3
⇒ y = −2
6. Find the value of p for which A(−1,3), B(2,p) and C(5,−1) are collinear.
Options: (a) 1 (b) −1 (c) 2 (d) −2
Ans: (a) 1
Soln
Slope AC = −2/3, Slope AB = (p−3)/3
p−3â/3 = −2/3 â⇒ p = 1
7. What is the midpoint of the line joining (−3,4) and (10,−5) ?
Options: (a) (−13,−9) (b) (−6.5,−4.5) (c) (3.5,−0.5) (d) none
Ans: (c) (3.5, −0.5)
Soln
M = (−3+10â/2 , 4−5/2â) = (3.5, −0.5)
8. A line passes through (3,4) and (5,6). Find the ordinate of the point whose abscissa is −1.
Options: (a) 1 (b) −1 (c) 2 (d) 0
Ans: (d) 0
Soln
Slope = 1 ⇒ Equation: y = x + 1
x = −1 ⇒ y = 0
9. If the distance between (8,p) and (4,3) is 5, find p.
Options: (a) 6 (b) 0 (c) both (a) and (b) (d) none
Ans: (c) both
Soln
(8 - 4)2 + (p - 3)2=25 ⇒ (p - 3)2 = 9 ⇒ p = 6 or 0
(8,p) āĻā§°ā§ (4,3) āĻŽāĻžāĻā§° āĻĻā§ā§°āϤā§āĻŦ 5 āĻšāϞ⧠p ā§° āĻŽāĻžāύ āĻāĻŋāĻŽāĻžāύ ?
10. Find the fourth vertex of a rectangle whose three vertices in order are (4,1), (7,4) and (13,−2).
Options: (a) (10,−5) (b) (10,5) (c) (8,3) (d) (8,−3)
Ans: (a) (10, −5)
Soln
D = A + C − B = (4,1) + (13,-2) - (7,4) = (10,-5)
11. If four vertices of a parallelogram in order are (−3,−1), (a,b), (3,3) and (4,3), find a:b.
Options: (a) 1:4 (b) 4:1 (c) 1:2 (d) 2:1
Ans: (b) 4 : 1
Soln
Diagonal midpoints equal (āĻĻā§āĻāĻž āĻā§°ā§āĻŖā§° āĻŽāϧā§āϝāĻŦāĻŋāύā§āĻĻā§ āĻāĻā§ āĻšāϝāĻŧāĨ¤) ⇒ a = −4, b = −1 ⇒ a:b = 4:1
12. Find the area of the triangle formed by (1,4), (3,2) and (−3,16).
Options: (a) 40 (b) 48 (c) 24 (d) none
Ans: (d) none
Soln
Area = 8 sq units, āϝāĻŋ āĻŦāĻŋāĻāϞā§āĻĒāϤ āύāĻžāĻāĨ¤
Let the three points be : A(1, 4), B(3, 2), C(−3, 16)
1st: Use the area formula of a triangle: Area = 1/2âŖx1(y2−y3)+x2(y3−y1)+x3(y1−y2)âŖ
2nd : Substitute the values
=1/2[1(2 -16) + 3(16 - 4) + (−3)(4−2)]
3rd: Simplify
=1/2[1(-14)+3(12)+(−3)(2)]
= 1/2â[−14+36−6]
= 1/2â*16
Ans: Area = 8 square units
13. The points (2,5), (4,1) and (6,−7) form which type of triangle ?
Options: (a) isosceles (b) equilateral (c) scalene (d) right-angled
Ans: (c) scalene
Soln
āϤāĻŋāύāĻŋāĻ āĻŦāĻžāĻšā§ā§° āĻĻā§ā§°ā§āĻā§āϝ āĻāĻŋāύā§āύ ⇒ Scalene triangle
14. Area = 70 sq units
The area of the triangle formed by (p, 2−2p), (1−p,2p) and (−4−p, 6−2p) is 70 sq units. How many integral values of p are possible ?
Options: (a) 2 (b) 3 (c) 4 (d) none
Ans: (a) 2
Soln
âŖ14(p - 4)âŖ = 70 ⇒âŖp−4âŖ = 5
p = 9 āĻŦāĻž −1
⇒ 2 values
15. If the origin is the midpoint of the line joining (2,3) and (x,y), find (x,y).
Options: (a) (2,-3) (b) (2,3) (c) (-2,3) (d) (-2,-3)
Ans: (d) (-2, -3)
Soln
2 + xâ / 2 = 0 ⇒ x = −2,
3 + y / 2 â= 0 ⇒y = −3