Angles and Triangles Worksheet for Maths Olympiad

Maths Olympiad topic 21: Angles and triangles · Set 138 · 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. One of the angles is 145°. What is the angle next to it on the same straight line? (a) 215° (b) 145° (c) 36° (d) 35°
2. 2.Two angles of a triangle are 30° and 130°. What is the third angle? (a) 150° (b) 20° (c) 160° (d) 50°
3. 3.Two straight lines cross. One of the angles is 80°. What is the angle next to it on the same straight line? (a) 80° (b) 280° (c) 10° (d) 100°
4. 4.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles? (a) 46° (b) 55° (c) 45° (d) 90°
5. 5.Two angles of a triangle are 75° and 45°. What is the third angle? (a) 105° (b) 60° (c) 135° (d) 120°
6. 6.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles? (a) 80° (b) 50° (c) 100° (d) 40°
7. 7.Two angles of a triangle are 30° and 55°. What is the third angle? (a) 150° (b) 85° (c) 125° (d) 95°
8. 8.Two angles of a triangle are 65° and 65°. What is the third angle? (a) 115° (b) 50° (c) 230° (d) 130°
9. 9.Two angles of a triangle are 75° and 20°. What is the exterior angle at the third corner? (a) 85° (b) 95° (c) 160° (d) 105°
10. 10.Two straight lines cross. One of the angles is 85°. What is the angle next to it on the same straight line? (a) 5° (b) 275° (c) 85° (d) 95°
11. 11.Two angles of a triangle are 30° and 95°. What is the exterior angle at the third corner? (a) 85° (b) 55° (c) 125° (d) 150°
12. 12.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles? (a) 110° (b) 35° (c) 45° (d) 70°
13. 13.Two angles of a triangle are 40° and 50°. What is the exterior angle at the third corner? (a) 140° (b) 130° (c) 270° (d) 90°
14. 14.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles? (a) 30° (b) 15° (c) 150° (d) 25°
15. 15.Two angles of a triangle are 20° and 140°. What is the third angle? (a) 160° (b) 40° (c) 200° (d) 20°
16. 16.Two straight lines cross. Two vertically opposite angles add up to 40°. What is each of the other two angles? (a) 320° (b) 140° (c) 20° (d) 160°
17. 17.Two angles of a triangle are 60° and 60°. What is the exterior angle at the third corner? (a) 121° (b) 60° (c) 120° (d) 240°
18. 18.Two angles of a triangle are 75° and 35°. What is the third angle? (a) 145° (b) 110° (c) 70° (d) 105°
19. 19.In an isosceles triangle, the two equal angles are 60° each. What is the third angle? (a) 30° (b) 120° (c) 61° (d) 60°
20. 20.Two straight lines cross. One of the angles is 20°. What is the angle next to it on the same straight line? (a) 20° (b) 340° (c) 160° (d) 70°
21. 21.Two angles of a triangle are 50° and 75°. What is the exterior angle at the third corner? (a) 105° (b) 55° (c) 125° (d) 130°
22. 22.Two angles of a triangle are 35° and 105°. What is the exterior angle at the third corner? (a) 75° (b) 145° (c) 140° (d) 40°
23. 23.Two straight lines cross. One of the angles is 55°. What is the angle next to it on the same straight line? (a) 125° (b) 305° (c) 35° (d) 55°
24. 24.Two angles of a triangle are 30° and 85°. What is the exterior angle at the third corner? (a) 65° (b) 150° (c) 115° (d) 95°
25. 25.Two straight lines cross. Two vertically opposite angles add up to 130°. What is each of the other two angles? (a) 50° (b) 115° (c) 230° (d) 65°
26. 26.Two angles of a triangle are 60° and 25°. What is the third angle? (a) 155° (b) 85° (c) 95° (d) 120°
27. 27.Two angles of a triangle are 50° and 60°. What is the third angle? (a) 120° (b) 130° (c) 70° (d) 110°
28. 28.Two straight lines cross. Two vertically opposite angles add up to 120°. What is each of the other two angles? (a) 60° (b) 120° (c) 121° (d) 240°
29. 29.Two straight lines cross. One of the angles is 110°. What is the angle next to it on the same straight line? (a) 110° (b) 71° (c) 70° (d) 250°
30. 30.In an isosceles triangle, the two equal angles are 55° each. What is the third angle? (a) 125° (b) 70° (c) 55° (d) 35°
31. 31.Two angles of a triangle are 45° and 45°. What is the third angle? (a) 91° (b) 135° (c) 270° (d) 90°
32. 32.Two angles of a triangle are 65° and 20°. What is the third angle? (a) 85° (b) 95° (c) 160° (d) 115°
33. 33.Two angles of a triangle are 80° and 70°. What is the third angle? (a) 100° (b) 110° (c) 30° (d) 150°
34. 34.Two angles of a triangle are 75° and 55°. What is the third angle? (a) 50° (b) 105° (c) 125° (d) 130°
35. 35.Two angles of a triangle are 80° and 40°. What is the exterior angle at the third corner? (a) 60° (b) 140° (c) 100° (d) 120°
36. 36.Two angles of a triangle are 25° and 35°. What is the third angle? (a) 145° (b) 60° (c) 155° (d) 120°
37. 37.Two straight lines cross. Two vertically opposite angles add up to 290°. What is each of the other two angles? (a) 35° (b) 145° (c) 70° (d) 36°
38. 38.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles? (a) 160° (b) 20° (c) 70° (d) 80°
39. 39.Two angles of a triangle are 80° and 70°. What is the exterior angle at the third corner? (a) 150° (b) 30° (c) 110° (d) 100°
40. 40.Two angles of a triangle are 75° and 95°. What is the third angle? (a) 10° (b) 105° (c) 170° (d) 85°

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