Angles and Triangles Worksheet for Maths Olympiad

Maths Olympiad topic 21: Angles and triangles · Set 803 · 40 questions

How to solve it (180 is the magic number): The three angles of a triangle add up to 180°. An exterior angle equals the sum of the two interior angles opposite it. An isosceles triangle has two equal angles, opposite its two equal sides. Angles on a straight line add up to 180°; vertically opposite angles are equal.

1. 1.Two angles of a triangle are 30° and 95°. What is the third angle? (a) 55° (b) 150° (c) 125° (d) 85°
2. 2.Two straight lines cross. Two vertically opposite angles add up to 130°. What is each of the other two angles? (a) 50° (b) 65° (c) 230° (d) 115°
3. 3.Two straight lines cross. Two vertically opposite angles add up to 280°. What is each of the other two angles? (a) 40° (b) 80° (c) 140° (d) 41°
4. 4.Two angles of a triangle are 75° and 65°. What is the third angle? (a) 40° (b) 115° (c) 105° (d) 140°
5. 5.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles? (a) 70° (b) 30° (c) 120° (d) 60°
6. 6.Two straight lines cross. Two vertically opposite angles add up to 250°. What is each of the other two angles? (a) 55° (b) 110° (c) 125° (d) 56°
7. 7.Two straight lines cross. One of the angles is 165°. What is the angle next to it on the same straight line? (a) 195° (b) 165° (c) 16° (d) 15°
8. 8.Two angles of a triangle are 30° and 25°. What is the exterior angle at the third corner? (a) 55° (b) 150° (c) 155° (d) 125°
9. 9.Two straight lines cross. One of the angles is 100°. What is the angle next to it on the same straight line? (a) 81° (b) 80° (c) 100° (d) 260°
10. 10.Two straight lines cross. One of the angles is 70°. What is the angle next to it on the same straight line? (a) 110° (b) 290° (c) 70° (d) 20°
11. 11.Two straight lines cross. One of the angles is 50°. What is the angle next to it on the same straight line? (a) 40° (b) 50° (c) 310° (d) 130°
12. 12.Two angles of a triangle are 20° and 80°. What is the third angle? (a) 160° (b) 80° (c) 260° (d) 100°
13. 13.Two angles of a triangle are 30° and 70°. What is the exterior angle at the third corner? (a) 150° (b) 80° (c) 100° (d) 110°
14. 14.Two angles of a triangle are 55° and 65°. What is the exterior angle at the third corner? (a) 115° (b) 120° (c) 60° (d) 125°
15. 15.Two angles of a triangle are 70° and 55°. What is the third angle? (a) 125° (b) 110° (c) 235° (d) 55°
16. 16.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles? (a) 55° (b) 70° (c) 110° (d) 20°
17. 17.Two straight lines cross. Two vertically opposite angles add up to 70°. What is each of the other two angles? (a) 110° (b) 35° (c) 145° (d) 290°
18. 18.Two angles of a triangle are 25° and 125°. What is the exterior angle at the third corner? (a) 30° (b) 155° (c) 55° (d) 150°
19. 19.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles? (a) 11° (b) 160° (c) 20° (d) 10°
20. 20.Two angles of a triangle are 60° and 25°. What is the exterior angle at the third corner? (a) 120° (b) 95° (c) 155° (d) 85°
21. 21.Two straight lines cross. Two vertically opposite angles add up to 90°. What is each of the other two angles? (a) 270° (b) 135° (c) 90° (d) 45°
22. 22.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles? (a) 130° (b) 50° (c) 35° (d) 25°
23. 23.Two angles of a triangle are 40° and 70°. What is the third angle? (a) 70° (b) 140° (c) 110° (d) 250°
24. 24.Two angles of a triangle are 80° and 45°. What is the third angle? (a) 55° (b) 135° (c) 100° (d) 125°
25. 25.In an isosceles triangle, the two equal angles are 70° each. What is the third angle? (a) 70° (b) 20° (c) 40° (d) 110°
26. 26.Two angles of a triangle are 55° and 50°. What is the exterior angle at the third corner? (a) 130° (b) 105° (c) 125° (d) 75°
27. 27.Two angles of a triangle are 40° and 45°. What is the third angle? (a) 140° (b) 135° (c) 85° (d) 95°
28. 28.Two angles of a triangle are 25° and 105°. What is the exterior angle at the third corner? (a) 75° (b) 155° (c) 130° (d) 50°
29. 29.Two angles of a triangle are 35° and 50°. What is the exterior angle at the third corner? (a) 130° (b) 95° (c) 145° (d) 85°
30. 30.In an isosceles triangle, the two equal angles are 65° each. What is the third angle? (a) 115° (b) 50° (c) 65° (d) 25°
31. 31.Two straight lines cross. One of the angles is 125°. What is the angle next to it on the same straight line? (a) 125° (b) 55° (c) 56° (d) 235°
32. 32.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles? (a) 130° (b) 50° (c) 40° (d) 65°
33. 33.Two straight lines cross. One of the angles is 95°. What is the angle next to it on the same straight line? (a) 95° (b) 86° (c) 85° (d) 265°
34. 34.Two angles of a triangle are 45° and 125°. What is the third angle? (a) 170° (b) 55° (c) 135° (d) 10°
35. 35.Two angles of a triangle are 55° and 25°. What is the third angle? (a) 100° (b) 125° (c) 155° (d) 80°
36. 36.Two angles of a triangle are 75° and 45°. What is the exterior angle at the third corner? (a) 135° (b) 120° (c) 60° (d) 105°
37. 37.Two angles of a triangle are 20° and 50°. What is the third angle? (a) 110° (b) 130° (c) 70° (d) 160°
38. 38.Two straight lines cross. One of the angles is 60°. What is the angle next to it on the same straight line? (a) 60° (b) 120° (c) 30° (d) 300°
39. 39.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles? (a) 80° (b) 70° (c) 20° (d) 160°
40. 40.Two straight lines cross. One of the angles is 160°. What is the angle next to it on the same straight line? (a) 200° (b) 20° (c) 21° (d) 160°

Free maths olympiad lessons, practice and worksheets at talentjr.in/maths-olympiad