Angles and Triangles Worksheet for Maths Olympiad

Maths Olympiad topic 21: Angles and triangles · Set 949 · 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 straight lines cross. Two vertically opposite angles add up to 80°. What is each of the other two angles? (a) 40° (b) 280° (c) 140° (d) 100°
2. 2.Two angles of a triangle are 80° and 35°. What is the third angle? (a) 100° (b) 65° (c) 145° (d) 115°
3. 3.In an isosceles triangle, the two equal angles are 35° each. What is the third angle? (a) 55° (b) 35° (c) 110° (d) 145°
4. 4.Two angles of a triangle are 40° and 55°. What is the third angle? (a) 95° (b) 125° (c) 85° (d) 140°
5. 5.Two angles of a triangle are 25° and 30°. What is the exterior angle at the third corner? (a) 155° (b) 150° (c) 55° (d) 125°
6. 6.Two straight lines cross. One of the angles is 80°. What is the angle next to it on the same straight line? (a) 100° (b) 80° (c) 10° (d) 280°
7. 7.Two angles of a triangle are 60° and 65°. What is the exterior angle at the third corner? (a) 55° (b) 115° (c) 125° (d) 120°
8. 8.Two angles of a triangle are 70° and 40°. What is the third angle? (a) 250° (b) 140° (c) 70° (d) 110°
9. 9.Two straight lines cross. Two vertically opposite angles add up to 140°. What is each of the other two angles? (a) 40° (b) 70° (c) 110° (d) 220°
10. 10.Two angles of a triangle are 80° and 50°. What is the third angle? (a) 230° (b) 100° (c) 130° (d) 50°
11. 11.Two angles of a triangle are 75° and 65°. What is the third angle? (a) 115° (b) 105° (c) 140° (d) 40°
12. 12.Two angles of a triangle are 25° and 110°. What is the exterior angle at the third corner? (a) 155° (b) 45° (c) 135° (d) 70°
13. 13.Two angles of a triangle are 50° and 35°. What is the exterior angle at the third corner? (a) 85° (b) 95° (c) 130° (d) 145°
14. 14.Two straight lines cross. One of the angles is 95°. What is the angle next to it on the same straight line? (a) 86° (b) 85° (c) 265° (d) 95°
15. 15.Two angles of a triangle are 20° and 105°. What is the exterior angle at the third corner? (a) 125° (b) 75° (c) 160° (d) 55°
16. 16.Two angles of a triangle are 65° and 65°. What is the exterior angle at the third corner? (a) 230° (b) 115° (c) 130° (d) 50°
17. 17.Two angles of a triangle are 25° and 140°. What is the third angle? (a) 155° (b) 165° (c) 15° (d) 40°
18. 18.Two straight lines cross. One of the angles is 140°. What is the angle next to it on the same straight line? (a) 40° (b) 41° (c) 220° (d) 140°
19. 19.Two straight lines cross. One of the angles is 55°. What is the angle next to it on the same straight line? (a) 55° (b) 305° (c) 35° (d) 125°
20. 20.Two angles of a triangle are 25° and 125°. What is the exterior angle at the third corner? (a) 55° (b) 150° (c) 155° (d) 30°
21. 21.Two angles of a triangle are 20° and 70°. What is the third angle? (a) 270° (b) 110° (c) 90° (d) 160°
22. 22.Two straight lines cross. One of the angles is 130°. What is the angle next to it on the same straight line? (a) 50° (b) 130° (c) 230° (d) 51°
23. 23.Two angles of a triangle are 50° and 35°. What is the third angle? (a) 145° (b) 95° (c) 130° (d) 85°
24. 24.Two straight lines cross. One of the angles is 45°. What is the angle next to it on the same straight line? (a) 45° (b) 135° (c) 136° (d) 315°
25. 25.Two angles of a triangle are 55° and 40°. What is the third angle? (a) 140° (b) 125° (c) 85° (d) 95°
26. 26.Two angles of a triangle are 55° and 105°. What is the third angle? (a) 160° (b) 125° (c) 75° (d) 20°
27. 27.Two angles of a triangle are 60° and 110°. What is the third angle? (a) 120° (b) 10° (c) 70° (d) 170°
28. 28.Two straight lines cross. Two vertically opposite angles add up to 280°. What is each of the other two angles? (a) 80° (b) 41° (c) 40° (d) 140°
29. 29.Two straight lines cross. One of the angles is 155°. What is the angle next to it on the same straight line? (a) 155° (b) 26° (c) 205° (d) 25°
30. 30.In an isosceles triangle, the two equal angles are 50° each. What is the third angle? (a) 40° (b) 130° (c) 50° (d) 80°
31. 31.In an isosceles triangle, the two equal angles are 80° each. What is the third angle? (a) 10° (b) 20° (c) 80° (d) 100°
32. 32.Two angles of a triangle are 80° and 70°. What is the exterior angle at the third corner? (a) 30° (b) 110° (c) 150° (d) 100°
33. 33.Two straight lines cross. One of the angles is 75°. What is the angle next to it on the same straight line? (a) 15° (b) 285° (c) 105° (d) 75°
34. 34.Two angles of a triangle are 30° and 80°. What is the exterior angle at the third corner? (a) 150° (b) 100° (c) 110° (d) 70°
35. 35.Two angles of a triangle are 40° and 100°. What is the exterior angle at the third corner? (a) 40° (b) 220° (c) 140° (d) 80°
36. 36.Two angles of a triangle are 25° and 30°. What is the third angle? (a) 150° (b) 155° (c) 125° (d) 55°
37. 37.Two angles of a triangle are 50° and 115°. What is the third angle? (a) 65° (b) 15° (c) 130° (d) 165°
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) 30° (b) 60° (c) 300° (d) 120°
39. 39.Two angles of a triangle are 35° and 95°. What is the third angle? (a) 130° (b) 85° (c) 145° (d) 50°
40. 40.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles? (a) 70° (b) 20° (c) 110° (d) 55°

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