Learn › Class 9 CBSE · Mathematics › Lines and Angles
Lines and Angles — Class 9 CBSE Mathematics MCQs with Solutions
Free Class 9 CBSE Mathematics Lines and Angles MCQs with step-by-step solutions. Practise online on Prepizo — no login needed.
▶ Practise Lines and Angles online (free)
Sample questions with solutions
Q1 — easy
If two complementary angles are in the ratio 2 : 3, the angles are:
A. 36° and 54° ✓ Correct
B. 40° and 50°
C. 72° and 108°
D. 30° and 60°
Solution: 2x + 3x = 90° → 5x = 90° → x = 18°. Angles: 36° and 54°.
Q2 — easy
An angle is 20° more than its supplement. The angle is:
A. 80°
B. 100° ✓ Correct
C. 110°
D. 70°
Solution: x + (x − 20°) = 180° → 2x = 200° → x = 100°.
Q3 — easy
If two parallel lines are cut by a transversal, alternate interior angles are:
A. Supplementary
B. Complementary
C. Equal ✓ Correct
D. Unequal
Solution: Alternate interior angles are equal for parallel lines.
Q4 — easy
In a triangle ABC, if ∠A + ∠B = 120°, then ∠C =
A. 50°
B. 60° ✓ Correct
C. 70°
D. 80°
Solution: 180° − 120° = 60°.
Q5 — easy
If measure of an angle is thrice its complement, the angle is:
A. 45°
B. 67.5° ✓ Correct
C. 60°
D. 22.5°
Solution: x = 3(90° − x) → 4x = 270° → x = 67.5°.
Q6 — easy
Angles forming a linear pair are always:
A. Complementary
B. Supplementary ✓ Correct
C. Equal
D. Right angles
Solution: Linear pair sum = 180° (supplementary).
Q7 — easy
If two interior angles on the same side of a transversal cutting parallel lines are in ratio 4 : 5, the smaller angle is:
A. 80° ✓ Correct
B. 100°
C. 40°
D. 90°
Solution: 4x + 5x = 180° → 9x = 180° → x = 20°. Smaller angle = 4(20°) = 80°.
Q8 — easy
If two lines intersect and one vertically opposite angle is 45°, adjacent angle in linear pair is:
A. 45°
B. 135° ✓ Correct
C. 90°
D. 180°
Solution: 180° − 45° = 135°.
Q9 — easy
Sum of all interior angles around a point on one side of a straight line is:
A. 90°
B. 180° ✓ Correct
C. 360°
D. 270°
Solution: Angles on a straight line add up to 180°.
Q10 — easy
Sum of all angles around a point is:
A. 180°
B. 270°
C. 360° ✓ Correct
D. 540°
Solution: Angles around a complete point sum to 360°.
Q11 — easy
In △ABC, side BC is produced to D. If exterior angle ∠ACD = 110° and ∠A = 60°, then ∠B =
A. 50° ✓ Correct
B. 60°
C. 70°
D. 40°
Solution: Exterior angle = ∠A + ∠B → 110° = 60° + ∠B → ∠B = 50°.
Q12 — easy
Can a triangle have two obtuse interior angles?
A. Yes
B. No ✓ Correct
C. Sometimes
D. Always
Solution: Sum of two obtuse angles > 180°, violating triangle angle sum property.
Q13 — easy
An exterior angle of a triangle is always _______ than either of its interior opposite angles.
A. Smaller
B. Equal
C. Greater ✓ Correct
D. Half
Solution: Exterior angle = sum of two interior opposite angles, so it is greater than either.
Q14 — easy
If three angles of a triangle are in ratio 1 : 2 : 3, the triangle is:
A. Acute angled
B. Right angled ✓ Correct
C. Obtuse angled
D. Equilateral
Solution: x + 2x + 3x = 180° → 6x = 180° → x = 30°. Angles: 30°, 60°, 90° (Right angled).
Q15 — easy
Value of x in figure where 2x and 3x form a linear pair on a straight line is:
A. 36° ✓ Correct
B. 18°
C. 45°
D. 30°
Solution: 2x + 3x = 180° → 5x = 180° → x = 36°.