← Angles and triangles lesson New set →

Angles and Triangles Worksheet for Maths Olympiad

Maths Olympiad topic 21: Angles and triangles · Set 110 · 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 25° and 125°. What is the third angle? (a) 55° (b) 150° (c) 30° (d) 155°
  2. 2.Two angles of a triangle are 30° and 45°. What is the exterior angle at the third corner? (a) 150° (b) 135° (c) 75° (d) 105°
  3. 3.Two angles of a triangle are 55° and 35°. What is the exterior angle at the third corner? (a) 125° (b) 145° (c) 90° (d) 270°
  4. 4.Two angles of a triangle are 20° and 25°. What is the exterior angle at the third corner? (a) 135° (b) 45° (c) 160° (d) 155°
  5. 5.Two straight lines cross. Two vertically opposite angles add up to 170°. What is each of the other two angles? (a) 10° (b) 190° (c) 95° (d) 85°
  6. 6.Two angles of a triangle are 60° and 65°. What is the exterior angle at the third corner? (a) 120° (b) 115° (c) 55° (d) 125°
  7. 7.Two angles of a triangle are 70° and 60°. What is the exterior angle at the third corner? (a) 50° (b) 110° (c) 120° (d) 130°
  8. 8.Two angles of a triangle are 35° and 85°. What is the exterior angle at the third corner? (a) 95° (b) 145° (c) 60° (d) 120°
  9. 9.Two angles of a triangle are 40° and 30°. What is the exterior angle at the third corner? (a) 150° (b) 70° (c) 140° (d) 110°
  10. 10.Two angles of a triangle are 25° and 130°. What is the third angle? (a) 155° (b) 25° (c) 205° (d) 50°
  11. 11.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles? (a) 160° (b) 80° (c) 70° (d) 20°
  12. 12.In an isosceles triangle, the two equal angles are 30° each. What is the third angle? (a) 60° (b) 150° (c) 30° (d) 120°
  13. 13.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles? (a) 60° (b) 30° (c) 120° (d) 70°
  14. 14.Two angles of a triangle are 30° and 80°. What is the third angle? (a) 100° (b) 150° (c) 70° (d) 110°
  15. 15.Two angles of a triangle are 20° and 75°. What is the third angle? (a) 95° (b) 105° (c) 160° (d) 85°
  16. 16.Two straight lines cross. Two vertically opposite angles add up to 140°. What is each of the other two angles? (a) 70° (b) 110° (c) 220° (d) 40°
  17. 17.Two angles of a triangle are 60° and 25°. What is the third angle? (a) 85° (b) 155° (c) 95° (d) 120°
  18. 18.Two angles of a triangle are 45° and 125°. What is the third angle? (a) 170° (b) 55° (c) 135° (d) 10°
  19. 19.Two angles of a triangle are 50° and 80°. What is the third angle? (a) 130° (b) 230° (c) 100° (d) 50°
  20. 20.Two angles of a triangle are 65° and 20°. What is the third angle? (a) 160° (b) 115° (c) 85° (d) 95°
  21. 21.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles? (a) 100° (b) 80° (c) 10° (d) 50°
  22. 22.Two angles of a triangle are 75° and 50°. What is the third angle? (a) 105° (b) 130° (c) 55° (d) 125°
  23. 23.Two angles of a triangle are 65° and 75°. What is the third angle? (a) 140° (b) 115° (c) 105° (d) 40°
  24. 24.In an isosceles triangle, the two equal angles are 70° each. What is the third angle? (a) 20° (b) 70° (c) 110° (d) 40°
  25. 25.Two angles of a triangle are 65° and 70°. What is the exterior angle at the third corner? (a) 110° (b) 135° (c) 45° (d) 115°
  26. 26.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles? (a) 35° (b) 50° (c) 130° (d) 25°
  27. 27.Two angles of a triangle are 65° and 85°. What is the exterior angle at the third corner? (a) 95° (b) 30° (c) 115° (d) 150°
  28. 28.Two angles of a triangle are 30° and 35°. What is the third angle? (a) 65° (b) 150° (c) 115° (d) 145°
  29. 29.Two angles of a triangle are 45° and 30°. What is the exterior angle at the third corner? (a) 105° (b) 150° (c) 135° (d) 75°
  30. 30.Two straight lines cross. One of the angles is 130°. What is the angle next to it on the same straight line? (a) 230° (b) 51° (c) 130° (d) 50°
  31. 31.Two straight lines cross. Two vertically opposite angles add up to 80°. What is each of the other two angles? (a) 40° (b) 100° (c) 140° (d) 280°
  32. 32.In an isosceles triangle, the two equal angles are 65° each. What is the third angle? (a) 65° (b) 115° (c) 25° (d) 50°
  33. 33.In an isosceles triangle, the two equal angles are 75° each. What is the third angle? (a) 105° (b) 30° (c) 15° (d) 75°
  34. 34.Two angles of a triangle are 20° and 55°. What is the third angle? (a) 105° (b) 75° (c) 125° (d) 160°
  35. 35.Two straight lines cross. One of the angles is 115°. What is the angle next to it on the same straight line? (a) 66° (b) 115° (c) 245° (d) 65°
  36. 36.Two straight lines cross. Two vertically opposite angles add up to 130°. What is each of the other two angles? (a) 50° (b) 230° (c) 65° (d) 115°
  37. 37.Two angles of a triangle are 75° and 25°. What is the third angle? (a) 105° (b) 80° (c) 155° (d) 100°
  38. 38.Two angles of a triangle are 55° and 20°. What is the exterior angle at the third corner? (a) 125° (b) 160° (c) 75° (d) 105°
  39. 39.Two angles of a triangle are 65° and 95°. What is the third angle? (a) 160° (b) 85° (c) 115° (d) 20°
  40. 40.Two angles of a triangle are 20° and 90°. What is the third angle? (a) 110° (b) 70° (c) 90° (d) 160°

Answer key

  1. 30°
  2. 75°
  3. 90°
  4. 45°
  5. 95°
  6. 125°
  7. 130°
  8. 120°
  9. 70°
  10. 25°
  11. 80°
  12. 120°
  13. 60°
  14. 70°
  15. 85°
  16. 110°
  17. 95°
  18. 10°
  19. 50°
  20. 95°
  21. 50°
  22. 55°
  23. 40°
  24. 40°
  25. 135°
  26. 25°
  27. 150°
  28. 115°
  29. 75°
  30. 50°
  31. 140°
  32. 50°
  33. 30°
  34. 105°
  35. 65°
  36. 115°
  37. 80°
  38. 75°
  39. 20°
  40. 70°

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