← Angles and triangles lesson New set →

Angles and Triangles Worksheet for Maths Olympiad

Maths Olympiad topic 21: Angles and triangles · Set 678 · 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 60° and 60°. What is the third angle? (a) 240° (b) 60° (c) 61° (d) 120°
  2. 2.Two angles of a triangle are 55° and 50°. What is the third angle? (a) 105° (b) 75° (c) 130° (d) 125°
  3. 3.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles? (a) 40° (b) 140° (c) 30° (d) 20°
  4. 4.Two angles of a triangle are 20° and 120°. What is the third angle? (a) 160° (b) 140° (c) 60° (d) 40°
  5. 5.Two angles of a triangle are 75° and 70°. What is the exterior angle at the third corner? (a) 35° (b) 105° (c) 145° (d) 110°
  6. 6.Two straight lines cross. One of the angles is 95°. What is the angle next to it on the same straight line? (a) 265° (b) 85° (c) 95° (d) 86°
  7. 7.Two angles of a triangle are 70° and 90°. What is the third angle? (a) 90° (b) 160° (c) 20° (d) 110°
  8. 8.Two angles of a triangle are 40° and 100°. What is the third angle? (a) 220° (b) 80° (c) 140° (d) 40°
  9. 9.Two angles of a triangle are 40° and 75°. What is the third angle? (a) 115° (b) 105° (c) 65° (d) 140°
  10. 10.Two straight lines cross. One of the angles is 135°. What is the angle next to it on the same straight line? (a) 46° (b) 225° (c) 135° (d) 45°
  11. 11.Two straight lines cross. Two vertically opposite angles add up to 160°. What is each of the other two angles? (a) 20° (b) 80° (c) 200° (d) 100°
  12. 12.In an isosceles triangle, the two equal angles are 35° each. What is the third angle? (a) 55° (b) 110° (c) 35° (d) 145°
  13. 13.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles? (a) 50° (b) 35° (c) 25° (d) 130°
  14. 14.Two angles of a triangle are 80° and 30°. What is the exterior angle at the third corner? (a) 100° (b) 110° (c) 70° (d) 150°
  15. 15.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles? (a) 80° (b) 100° (c) 50° (d) 40°
  16. 16.Two angles of a triangle are 50° and 120°. What is the third angle? (a) 170° (b) 60° (c) 130° (d) 10°
  17. 17.Two straight lines cross. One of the angles is 30°. What is the angle next to it on the same straight line? (a) 30° (b) 330° (c) 60° (d) 150°
  18. 18.Two angles of a triangle are 70° and 25°. What is the exterior angle at the third corner? (a) 85° (b) 110° (c) 155° (d) 95°
  19. 19.Two angles of a triangle are 20° and 65°. What is the exterior angle at the third corner? (a) 115° (b) 160° (c) 85° (d) 95°
  20. 20.Two straight lines cross. One of the angles is 120°. What is the angle next to it on the same straight line? (a) 120° (b) 60° (c) 240° (d) 61°
  21. 21.Two angles of a triangle are 80° and 55°. What is the third angle? (a) 45° (b) 135° (c) 100° (d) 125°
  22. 22.Two angles of a triangle are 35° and 55°. What is the exterior angle at the third corner? (a) 90° (b) 125° (c) 270° (d) 145°
  23. 23.Two angles of a triangle are 50° and 45°. What is the third angle? (a) 130° (b) 95° (c) 85° (d) 135°
  24. 24.Two angles of a triangle are 40° and 60°. What is the exterior angle at the third corner? (a) 140° (b) 120° (c) 100° (d) 80°
  25. 25.Two straight lines cross. Two vertically opposite angles add up to 40°. What is each of the other two angles? (a) 320° (b) 20° (c) 160° (d) 140°
  26. 26.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) 35° (c) 305° (d) 125°
  27. 27.Two angles of a triangle are 30° and 100°. What is the third angle? (a) 50° (b) 80° (c) 150° (d) 130°
  28. 28.Two angles of a triangle are 35° and 115°. What is the third angle? (a) 65° (b) 30° (c) 150° (d) 145°
  29. 29.Two angles of a triangle are 60° and 45°. What is the exterior angle at the third corner? (a) 120° (b) 75° (c) 105° (d) 135°
  30. 30.Two straight lines cross. One of the angles is 40°. What is the angle next to it on the same straight line? (a) 140° (b) 320° (c) 40° (d) 50°
  31. 31.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) 45° (d) 90°
  32. 32.Two angles of a triangle are 75° and 55°. What is the exterior angle at the third corner? (a) 105° (b) 50° (c) 125° (d) 130°
  33. 33.Two straight lines cross. One of the angles is 160°. What is the angle next to it on the same straight line? (a) 21° (b) 200° (c) 20° (d) 160°
  34. 34.Two angles of a triangle are 45° and 25°. What is the third angle? (a) 135° (b) 70° (c) 155° (d) 110°
  35. 35.Two angles of a triangle are 35° and 100°. What is the third angle? (a) 135° (b) 45° (c) 80° (d) 145°
  36. 36.In an isosceles triangle, the two equal angles are 80° each. What is the third angle? (a) 80° (b) 20° (c) 10° (d) 100°
  37. 37.Two angles of a triangle are 60° and 90°. What is the exterior angle at the third corner? (a) 90° (b) 30° (c) 120° (d) 150°
  38. 38.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) 235° (d) 56°
  39. 39.Two angles of a triangle are 70° and 35°. What is the third angle? (a) 105° (b) 75° (c) 145° (d) 110°
  40. 40.Two straight lines cross. One of the angles is 115°. What is the angle next to it on the same straight line? (a) 65° (b) 66° (c) 245° (d) 115°

Answer key

  1. 60°
  2. 75°
  3. 20°
  4. 40°
  5. 145°
  6. 85°
  7. 20°
  8. 40°
  9. 65°
  10. 45°
  11. 100°
  12. 110°
  13. 25°
  14. 110°
  15. 40°
  16. 10°
  17. 150°
  18. 95°
  19. 85°
  20. 60°
  21. 45°
  22. 90°
  23. 85°
  24. 100°
  25. 160°
  26. 125°
  27. 50°
  28. 30°
  29. 105°
  30. 140°
  31. 135°
  32. 130°
  33. 20°
  34. 110°
  35. 45°
  36. 20°
  37. 150°
  38. 55°
  39. 75°
  40. 65°

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