1. Two angles form a linear pair. One is 72°. Find the other.
- A108°
- B18°
- C72°
- D288°
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Answer: A) 108°
Linear pair sums to 180°. 180 − 72 = 108.
Class 9 Lines and Angles — practice questions with answers
Geometry — Lines and Angles · 5 sample questions from the school syllabus. Try each one, then open the answer and the worked solution.
2. Two angles are supplementary. One measures 95°. Find the other.
- A93
- B77
- C170
- D85
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Answer: D) 85
Supplementary angles sum to 180°. 180 − 95 = 85°.
3. The measure of an angle is three times its complement. Find the angle.
- A60.5
- B67.5
- C135
- D74.5
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Answer: B) 67.5
x = 3(90 − x) → x = 270 − 3x → 4x = 270 → x = 67.5°.
4. Two angles are in the ratio 7 : 2 and are complementary. Find the larger angle (in degrees).
- A63
- B77
- C70
- D140
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Answer: C) 70
7x + 2x = 90 → 9x = 90 → x = 10. Larger = 7x = 70°.
5. In ΔABC, side BC is extended to D. If ∠ABC = 55° and ∠ACD (exterior) = 120°, find ∠BAC.
- A59
- B65
- C71
- D130
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Answer: B) 65
Exterior angle = sum of two opposite interior angles. 120 = ∠ABC + ∠BAC = 55 + ∠BAC → ∠BAC = 65°.
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