← Angles and triangles lesson New set →

Angles and Triangles Worksheet for Maths Olympiad

Maths Olympiad topic 21: Angles and triangles · Set 28 · 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.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°
  2. 2.Two angles of a triangle are 40° and 40°. What is the exterior angle at the third corner? (a) 140° (b) 80° (c) 280° (d) 100°
  3. 3.Two straight lines cross. One of the angles is 45°. What is the angle next to it on the same straight line? (a) 136° (b) 135° (c) 45° (d) 315°
  4. 4.Two angles of a triangle are 55° and 45°. What is the third angle? (a) 100° (b) 80° (c) 135° (d) 125°
  5. 5.Two straight lines cross. Two vertically opposite angles add up to 290°. What is each of the other two angles? (a) 145° (b) 35° (c) 36° (d) 70°
  6. 6.Two angles of a triangle are 20° and 55°. What is the exterior angle at the third corner? (a) 125° (b) 160° (c) 105° (d) 75°
  7. 7.Two angles of a triangle are 50° and 110°. What is the third angle? (a) 160° (b) 130° (c) 70° (d) 20°
  8. 8.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles? (a) 35° (b) 25° (c) 50° (d) 130°
  9. 9.Two straight lines cross. Two vertically opposite angles add up to 200°. What is each of the other two angles? (a) 160° (b) 80° (c) 100° (d) 81°
  10. 10.Two angles of a triangle are 35° and 40°. What is the third angle? (a) 145° (b) 140° (c) 75° (d) 105°
  11. 11.Two angles of a triangle are 55° and 40°. What is the exterior angle at the third corner? (a) 95° (b) 85° (c) 140° (d) 125°
  12. 12.In an isosceles triangle, the two equal angles are 70° each. What is the third angle? (a) 40° (b) 70° (c) 110° (d) 20°
  13. 13.Two straight lines cross. One of the angles is 25°. What is the angle next to it on the same straight line? (a) 155° (b) 335° (c) 65° (d) 25°
  14. 14.Two angles of a triangle are 70° and 55°. What is the exterior angle at the third corner? (a) 235° (b) 110° (c) 125° (d) 55°
  15. 15.Two angles of a triangle are 20° and 35°. What is the exterior angle at the third corner? (a) 145° (b) 160° (c) 125° (d) 55°
  16. 16.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles? (a) 40° (b) 120° (c) 60° (d) 30°
  17. 17.Two angles of a triangle are 70° and 45°. What is the third angle? (a) 110° (b) 135° (c) 65° (d) 115°
  18. 18.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles? (a) 15° (b) 30° (c) 25° (d) 150°
  19. 19.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles? (a) 30° (b) 70° (c) 120° (d) 60°
  20. 20.Two straight lines cross. One of the angles is 60°. What is the angle next to it on the same straight line? (a) 300° (b) 30° (c) 60° (d) 120°
  21. 21.Two angles of a triangle are 50° and 90°. What is the exterior angle at the third corner? (a) 140° (b) 40° (c) 130° (d) 90°
  22. 22.Two angles of a triangle are 50° and 95°. What is the exterior angle at the third corner? (a) 145° (b) 35° (c) 130° (d) 85°
  23. 23.Two angles of a triangle are 45° and 75°. What is the exterior angle at the third corner? (a) 105° (b) 135° (c) 60° (d) 120°
  24. 24.Two angles of a triangle are 30° and 95°. What is the third angle? (a) 85° (b) 150° (c) 55° (d) 125°
  25. 25.In an isosceles triangle, the two equal angles are 25° each. What is the third angle? (a) 130° (b) 25° (c) 65° (d) 155°
  26. 26.Two angles of a triangle are 25° and 45°. What is the exterior angle at the third corner? (a) 135° (b) 155° (c) 70° (d) 110°
  27. 27.Two angles of a triangle are 25° and 65°. What is the third angle? (a) 115° (b) 90° (c) 270° (d) 155°
  28. 28.Two angles of a triangle are 65° and 85°. What is the exterior angle at the third corner? (a) 150° (b) 30° (c) 95° (d) 115°
  29. 29.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°
  30. 30.Two angles of a triangle are 45° and 30°. What is the third angle? (a) 75° (b) 135° (c) 150° (d) 105°
  31. 31.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) 71° (c) 110° (d) 250°
  32. 32.Two angles of a triangle are 35° and 25°. What is the third angle? (a) 60° (b) 120° (c) 145° (d) 155°
  33. 33.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°
  34. 34.In an isosceles triangle, the two equal angles are 40° each. What is the third angle? (a) 40° (b) 50° (c) 140° (d) 100°
  35. 35.Two angles of a triangle are 60° and 55°. What is the exterior angle at the third corner? (a) 125° (b) 120° (c) 115° (d) 65°
  36. 36.Two straight lines cross. One of the angles is 120°. What is the angle next to it on the same straight line? (a) 61° (b) 240° (c) 60° (d) 120°
  37. 37.Two angles of a triangle are 55° and 30°. What is the exterior angle at the third corner? (a) 125° (b) 95° (c) 85° (d) 150°
  38. 38.Two angles of a triangle are 30° and 25°. What is the exterior angle at the third corner? (a) 155° (b) 150° (c) 55° (d) 125°
  39. 39.In an isosceles triangle, the two equal angles are 30° each. What is the third angle? (a) 60° (b) 150° (c) 120° (d) 30°
  40. 40.Two angles of a triangle are 80° and 45°. What is the exterior angle at the third corner? (a) 100° (b) 55° (c) 135° (d) 125°

Answer key

  1. 80°
  2. 80°
  3. 135°
  4. 80°
  5. 35°
  6. 75°
  7. 20°
  8. 25°
  9. 80°
  10. 105°
  11. 95°
  12. 40°
  13. 155°
  14. 125°
  15. 55°
  16. 30°
  17. 65°
  18. 15°
  19. 60°
  20. 120°
  21. 140°
  22. 145°
  23. 120°
  24. 55°
  25. 130°
  26. 70°
  27. 90°
  28. 150°
  29. 40°
  30. 105°
  31. 70°
  32. 120°
  33. 85°
  34. 100°
  35. 115°
  36. 60°
  37. 85°
  38. 55°
  39. 120°
  40. 125°

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