1. Two angles are complementary if their measures add up to:
- A90°
- B180°
- C360°
- D45°
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Answer: A) 90°
By definition, two angles are complementary when their sum is exactly 90°.
Class 7 Complementary and Supplementary 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. Can an obtuse angle (greater than 90°) ever have a complement?
- ANo, because the complement would be negative
- BYes, always
- COnly if it is 100°
- DOnly if it is exactly 90°
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Answer: A) No, because the complement would be negative
Complement = 90° − angle. If the angle is more than 90°, the result is negative, which is not a valid angle. So obtuse angles have no complement.
3. Riya is drawing two angles on her geometry sheet. The first angle measures 34°. She wants the second angle to make the pair complementary. What should the second angle measure?
- A112
- B50
- C62
- D56
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Answer: D) 56
For a complementary pair the sum is 90°. Second angle = 90° − 34° = 56°.
4. Three angles together form a straight line, so their sum is 180°.
Two of them are 55° and 47°. The third angle is supplementary to which single angle?
Give the measure of that single angle.
Two of them are 55° and 47°. The third angle is supplementary to which single angle?
Give the measure of that single angle.
- A102
- B204
- C92
- D112
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Answer: A) 102
Third angle = 180° − 55° − 47° = 78°. The angle supplementary to 78° is 180° − 78° = 102°.
5. Angle P and angle Q are complementary, and angle Q and angle R are supplementary.
If angle R is 5 times angle P, find angle P.
If angle R is 5 times angle P, find angle P.
- A45
- B22.5
- C24.5
- D20.5
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Answer: B) 22.5
Q = 90° − P (complementary). R = 180° − Q = 180° − (90° − P) = 90° + P. Given R = 5P: 90° + P = 5P, so 4P = 90°, P = 22.5°.
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