← Angles and triangles lesson New set →

Angles and Triangles Worksheet for Maths Olympiad

Maths Olympiad topic 21: Angles and triangles · Set 685 · 40 questions
TalentJR

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.

NameDateTime takenScore ___ / 40
  1. 1.Two angles of a triangle are 75° and 35°. What is the exterior angle at the third corner? (a) 110° (b) 70° (c) 145° (d) 105°
  2. 2.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles? (a) 150° (b) 60° (c) 30° (d) 75°
  3. 3.Two angles of a triangle are 25° and 85°. What is the exterior angle at the third corner? (a) 110° (b) 95° (c) 155° (d) 70°
  4. 4.Two angles of a triangle are 65° and 20°. What is the third angle? (a) 85° (b) 160° (c) 95° (d) 115°
  5. 5.Two straight lines cross. One of the angles is 40°. What is the angle next to it on the same straight line? (a) 320° (b) 40° (c) 50° (d) 140°
  6. 6.Two angles of a triangle are 65° and 55°. What is the exterior angle at the third corner? (a) 115° (b) 125° (c) 60° (d) 120°
  7. 7.Two angles of a triangle are 60° and 85°. What is the third angle? (a) 120° (b) 95° (c) 145° (d) 35°
  8. 8.Two straight lines cross. Two vertically opposite angles add up to 120°. What is each of the other two angles? (a) 121° (b) 240° (c) 120° (d) 60°
  9. 9.Two angles of a triangle are 50° and 85°. What is the third angle? (a) 130° (b) 135° (c) 95° (d) 45°
  10. 10.In an isosceles triangle, the two equal angles are 35° each. What is the third angle? (a) 55° (b) 35° (c) 145° (d) 110°
  11. 11.Two angles of a triangle are 65° and 90°. What is the third angle? (a) 155° (b) 25° (c) 90° (d) 115°
  12. 12.Two angles of a triangle are 65° and 85°. What is the third angle? (a) 150° (b) 30° (c) 115° (d) 95°
  13. 13.Two straight lines cross. One of the angles is 110°. What is the angle next to it on the same straight line? (a) 70° (b) 110° (c) 71° (d) 250°
  14. 14.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles? (a) 40° (b) 65° (c) 130° (d) 50°
  15. 15.Two straight lines cross. One of the angles is 70°. What is the angle next to it on the same straight line? (a) 20° (b) 290° (c) 110° (d) 70°
  16. 16.Two straight lines cross. Two vertically opposite angles add up to 130°. What is each of the other two angles? (a) 115° (b) 230° (c) 65° (d) 50°
  17. 17.Two straight lines cross. Two vertically opposite angles add up to 330°. What is each of the other two angles? (a) 165° (b) 15° (c) 30° (d) 16°
  18. 18.Two angles of a triangle are 45° and 75°. What is the third angle? (a) 135° (b) 120° (c) 105° (d) 60°
  19. 19.In an isosceles triangle, the two equal angles are 75° each. What is the third angle? (a) 75° (b) 30° (c) 105° (d) 15°
  20. 20.Two angles of a triangle are 20° and 45°. What is the third angle? (a) 65° (b) 160° (c) 135° (d) 115°
  21. 21.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) 70° (d) 160°
  22. 22.Two angles of a triangle are 45° and 80°. What is the third angle? (a) 125° (b) 135° (c) 100° (d) 55°
  23. 23.Two angles of a triangle are 65° and 65°. What is the exterior angle at the third corner? (a) 50° (b) 115° (c) 230° (d) 130°
  24. 24.Two angles of a triangle are 65° and 60°. What is the exterior angle at the third corner? (a) 120° (b) 115° (c) 125° (d) 55°
  25. 25.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles? (a) 20° (b) 70° (c) 160° (d) 80°
  26. 26.In an isosceles triangle, the two equal angles are 80° each. What is the third angle? (a) 10° (b) 100° (c) 80° (d) 20°
  27. 27.Two angles of a triangle are 25° and 90°. What is the third angle? (a) 155° (b) 115° (c) 90° (d) 65°
  28. 28.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles? (a) 50° (b) 130° (c) 25° (d) 35°
  29. 29.In an isosceles triangle, the two equal angles are 65° each. What is the third angle? (a) 115° (b) 25° (c) 50° (d) 65°
  30. 30.Two angles of a triangle are 25° and 50°. What is the exterior angle at the third corner? (a) 105° (b) 130° (c) 155° (d) 75°
  31. 31.Two angles of a triangle are 80° and 35°. What is the third angle? (a) 100° (b) 115° (c) 145° (d) 65°
  32. 32.Two straight lines cross. Two vertically opposite angles add up to 260°. What is each of the other two angles? (a) 51° (b) 100° (c) 50° (d) 130°
  33. 33.Two angles of a triangle are 50° and 50°. What is the third angle? (a) 100° (b) 130° (c) 80° (d) 260°
  34. 34.Two angles of a triangle are 35° and 100°. What is the exterior angle at the third corner? (a) 45° (b) 145° (c) 135° (d) 80°
  35. 35.Two angles of a triangle are 65° and 30°. What is the third angle? (a) 95° (b) 150° (c) 115° (d) 85°
  36. 36.Two angles of a triangle are 45° and 55°. What is the third angle? (a) 80° (b) 125° (c) 135° (d) 100°
  37. 37.Two angles of a triangle are 35° and 90°. What is the third angle? (a) 55° (b) 90° (c) 145° (d) 125°
  38. 38.Two straight lines cross. Two vertically opposite angles add up to 140°. What is each of the other two angles? (a) 110° (b) 220° (c) 70° (d) 40°
  39. 39.Two angles of a triangle are 50° and 70°. What is the third angle? (a) 120° (b) 130° (c) 110° (d) 60°
  40. 40.Two straight lines cross. One of the angles is 75°. What is the angle next to it on the same straight line? (a) 285° (b) 105° (c) 15° (d) 75°

Answer key

  1. 110°
  2. 75°
  3. 110°
  4. 95°
  5. 140°
  6. 120°
  7. 35°
  8. 120°
  9. 45°
  10. 110°
  11. 25°
  12. 30°
  13. 70°
  14. 65°
  15. 110°
  16. 115°
  17. 15°
  18. 60°
  19. 30°
  20. 115°
  21. 160°
  22. 55°
  23. 130°
  24. 125°
  25. 80°
  26. 20°
  27. 65°
  28. 25°
  29. 50°
  30. 75°
  31. 65°
  32. 50°
  33. 80°
  34. 135°
  35. 85°
  36. 80°
  37. 55°
  38. 110°
  39. 60°
  40. 105°

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