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Mathematics · Year 8
Angles follow reliable rules that let you find a missing angle without measuring. The three angles inside any triangle always add up to 180°. The four angles inside any quadrilateral always add up to 360°. A right angle is exactly 90°.
Example
A triangle has angles of 60° and 70°. Since all three must add to 180°, the third angle is 180° − 60° − 70° = 50°.
Key terms
Questions
1. A right angle measures:
2. Angles on a straight line add up to:
3. A triangle has angles of 90° and 40°. The third angle is:
4. An angle less than 90° is called:
5. A full circle measures:
6. Two angles that add up to 90° are called:
7. Half of a right angle is:
8. A triangle has angles 60° and 70°. The third angle is:
9. Angles in a quadrilateral add up to:
10. An angle greater than 90° but less than 180° is called:
11. A triangle has angles of 45° and 55°. The third angle is:
12. A quadrilateral has three angles of 90° each. The fourth angle is:
13. Two angles that add up to 180° are called:
14. A quadrilateral has angles of 100°, 90° and 85°. The fourth angle is:
15. A triangle has one angle of 90° and another of 35°. The third angle is:
16. A quadrilateral has three angles of 100°, 80° and 95°. The fourth angle is:
17. An angle of 200° is called a:
18. Two angles are supplementary. One is 65°. The other is:
19. A triangle has two equal angles of 50° each. The third angle is:
20. A right-angled triangle has one other angle of 30°. The third angle is:
21. A quadrilateral's angles are in the ratio 1:1:2:2. The smallest angle is:
Answer key (parent copy)