1. Find the complement of 38°.
- A52°
- B142°
- C62°
- D38°
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Answer: A) 52°
Complementary angles sum to 90°. 90 − 38 = 52°.
Class 7 Lines and Angles — practice questions with answers
Lines and Angles · 5 sample questions from the school syllabus. Try each one, then open the answer and the worked solution.
2. Two lines intersect. One angle is 124°. Find the measure of one of the angles adjacent to it (its linear pair partner).
- A112
- B62
- C50
- D56
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Answer: D) 56
Adjacent angles form a linear pair summing to 180°. 180 − 124 = 56°.
3. Two angles are said to be a linear pair. If one angle is acute, what must the other angle be?
- AObtuse
- BAcute
- CRight
- DReflex
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Answer: A) Obtuse
A linear pair sums to 180°. If one is acute (< 90°), the other must be more than 90° (obtuse) to make the total 180°.
4. A transversal cuts two lines c and d. A pair of alternate exterior angles measures 117° and 63°. Are c and d parallel?
- AYes — 117 + 63 = 180°, and alternate exterior angles are supplementary.
- BYes — one angle is obtuse and the other acute, as parallel lines require.
- CNo — alternate exterior angles would have to be EQUAL, and 117 is not 63.
- DNo — the two angles would have to add up to 90°.
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Answer: C) No — alternate exterior angles would have to be EQUAL, and 117 is not 63.
Alternate exterior angles are equal when the lines are parallel. Here 117° and 63° are unequal, so c and d are not parallel. Trap: the first option borrows the CO-INTERIOR rule (sum 180°) and applies it to alternate exterior angles — the sum being 180° is exactly what tempts students here, but it proves nothing for this pair.
5. Which of these statements is FALSE?
- AA linear pair is always supplementary.
- BIf two angles are equal and supplementary, each of them must be acute.
- CAngles around a point add up to 360°.
- DCo-interior angles between two parallel lines add up to 180°.
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Answer: B) If two angles are equal and supplementary, each of them must be acute.
If two equal angles are supplementary, then x + x = 180, so each is 90° — a RIGHT angle, not an acute one. That statement is therefore false. The other three are all standard true results: linear pairs are supplementary, a full turn is 360°, and co-interior angles between parallels sum to 180°.
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