← Angles and triangles lesson New set →

Angles and Triangles Worksheet for Maths Olympiad

Maths Olympiad topic 21: Angles and triangles · Set 729 · 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 90°. What is each of the other two angles? (a) 46° (b) 55° (c) 45° (d) 90°
  2. 2.In an isosceles triangle, the two equal angles are 85° each. What is the third angle? (a) 95° (b) 85° (c) 10° (d) 5°
  3. 3.Two angles of a triangle are 25° and 140°. What is the third angle? (a) 165° (b) 15° (c) 40° (d) 155°
  4. 4.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles? (a) 130° (b) 65° (c) 40° (d) 50°
  5. 5.Two angles of a triangle are 80° and 25°. What is the exterior angle at the third corner? (a) 75° (b) 155° (c) 105° (d) 100°
  6. 6.Two straight lines cross. One of the angles is 140°. What is the angle next to it on the same straight line? (a) 41° (b) 40° (c) 220° (d) 140°
  7. 7.Two angles of a triangle are 25° and 20°. What is the exterior angle at the third corner? (a) 135° (b) 155° (c) 160° (d) 45°
  8. 8.Two straight lines cross. Two vertically opposite angles add up to 320°. What is each of the other two angles? (a) 160° (b) 40° (c) 20° (d) 21°
  9. 9.Two angles of a triangle are 55° and 60°. What is the exterior angle at the third corner? (a) 125° (b) 65° (c) 115° (d) 120°
  10. 10.Two angles of a triangle are 75° and 65°. What is the third angle? (a) 105° (b) 140° (c) 40° (d) 115°
  11. 11.Two angles of a triangle are 60° and 75°. What is the third angle? (a) 135° (b) 120° (c) 45° (d) 105°
  12. 12.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles? (a) 60° (b) 30° (c) 150° (d) 75°
  13. 13.Two angles of a triangle are 35° and 50°. What is the exterior angle at the third corner? (a) 85° (b) 145° (c) 130° (d) 95°
  14. 14.In an isosceles triangle, the two equal angles are 75° each. What is the third angle? (a) 75° (b) 30° (c) 15° (d) 105°
  15. 15.Two straight lines cross. Two vertically opposite angles add up to 250°. What is each of the other two angles? (a) 110° (b) 125° (c) 56° (d) 55°
  16. 16.Two angles of a triangle are 35° and 25°. What is the third angle? (a) 60° (b) 155° (c) 120° (d) 145°
  17. 17.Two angles of a triangle are 45° and 35°. What is the third angle? (a) 80° (b) 145° (c) 100° (d) 135°
  18. 18.Two angles of a triangle are 20° and 40°. What is the exterior angle at the third corner? (a) 120° (b) 160° (c) 60° (d) 140°
  19. 19.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) 40° (d) 50°
  20. 20.Two straight lines cross. One of the angles is 35°. What is the angle next to it on the same straight line? (a) 145° (b) 325° (c) 55° (d) 35°
  21. 21.Two straight lines cross. Two vertically opposite angles add up to 80°. What is each of the other two angles? (a) 140° (b) 280° (c) 100° (d) 40°
  22. 22.Two angles of a triangle are 35° and 100°. What is the third angle? (a) 135° (b) 80° (c) 45° (d) 145°
  23. 23.Two straight lines cross. Two vertically opposite angles add up to 200°. What is each of the other two angles? (a) 81° (b) 160° (c) 80° (d) 100°
  24. 24.Two straight lines cross. One of the angles is 130°. What is the angle next to it on the same straight line? (a) 51° (b) 130° (c) 230° (d) 50°
  25. 25.Two angles of a triangle are 25° and 65°. What is the exterior angle at the third corner? (a) 270° (b) 90° (c) 115° (d) 155°
  26. 26.Two angles of a triangle are 70° and 60°. What is the exterior angle at the third corner? (a) 120° (b) 130° (c) 50° (d) 110°
  27. 27.Two angles of a triangle are 65° and 50°. What is the third angle? (a) 115° (b) 65° (c) 130° (d) 245°
  28. 28.Two angles of a triangle are 55° and 75°. What is the third angle? (a) 130° (b) 105° (c) 125° (d) 50°
  29. 29.Two angles of a triangle are 50° and 70°. What is the third angle? (a) 110° (b) 60° (c) 130° (d) 120°
  30. 30.Two straight lines cross. One of the angles is 170°. What is the angle next to it on the same straight line? (a) 170° (b) 190° (c) 11° (d) 10°
  31. 31.Two angles of a triangle are 40° and 95°. What is the exterior angle at the third corner? (a) 135° (b) 45° (c) 140° (d) 85°
  32. 32.In an isosceles triangle, the two equal angles are 60° each. What is the third angle? (a) 120° (b) 30° (c) 61° (d) 60°
  33. 33.Two straight lines cross. One of the angles is 165°. What is the angle next to it on the same straight line? (a) 165° (b) 16° (c) 15° (d) 195°
  34. 34.Two angles of a triangle are 25° and 100°. What is the exterior angle at the third corner? (a) 125° (b) 80° (c) 155° (d) 55°
  35. 35.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) 35° (d) 25°
  36. 36.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles? (a) 140° (b) 20° (c) 30° (d) 40°
  37. 37.Two angles of a triangle are 80° and 50°. What is the third angle? (a) 100° (b) 230° (c) 50° (d) 130°
  38. 38.Two angles of a triangle are 65° and 55°. What is the exterior angle at the third corner? (a) 115° (b) 120° (c) 60° (d) 125°
  39. 39.Two angles of a triangle are 50° and 50°. What is the exterior angle at the third corner? (a) 260° (b) 100° (c) 130° (d) 80°
  40. 40.Two angles of a triangle are 40° and 50°. What is the exterior angle at the third corner? (a) 130° (b) 270° (c) 140° (d) 90°

Answer key

  1. 45°
  2. 10°
  3. 15°
  4. 65°
  5. 105°
  6. 40°
  7. 45°
  8. 20°
  9. 115°
  10. 40°
  11. 45°
  12. 75°
  13. 85°
  14. 30°
  15. 55°
  16. 120°
  17. 100°
  18. 60°
  19. 40°
  20. 145°
  21. 140°
  22. 45°
  23. 80°
  24. 50°
  25. 90°
  26. 130°
  27. 65°
  28. 50°
  29. 60°
  30. 10°
  31. 135°
  32. 60°
  33. 15°
  34. 125°
  35. 25°
  36. 20°
  37. 50°
  38. 120°
  39. 100°
  40. 90°

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