← Angles and triangles lesson New set →

Angles and Triangles Worksheet for Maths Olympiad

Maths Olympiad topic 21: Angles and triangles · Set 249 · 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 straight lines cross. One of the angles is 140°. What is the angle next to it on the same straight line? (a) 220° (b) 140° (c) 41° (d) 40°
  2. 2.Two angles of a triangle are 20° and 35°. What is the exterior angle at the third corner? (a) 145° (b) 160° (c) 55° (d) 125°
  3. 3.Two angles of a triangle are 45° and 125°. What is the third angle? (a) 135° (b) 170° (c) 10° (d) 55°
  4. 4.Two straight lines cross. One of the angles is 65°. What is the angle next to it on the same straight line? (a) 115° (b) 65° (c) 295° (d) 25°
  5. 5.Two straight lines cross. Two vertically opposite angles add up to 220°. What is each of the other two angles? (a) 110° (b) 140° (c) 71° (d) 70°
  6. 6.Two angles of a triangle are 50° and 85°. What is the exterior angle at the third corner? (a) 45° (b) 130° (c) 95° (d) 135°
  7. 7.Two angles of a triangle are 75° and 50°. What is the exterior angle at the third corner? (a) 55° (b) 125° (c) 130° (d) 105°
  8. 8.Two straight lines cross. One of the angles is 95°. What is the angle next to it on the same straight line? (a) 95° (b) 265° (c) 85° (d) 86°
  9. 9.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles? (a) 150° (b) 15° (c) 30° (d) 25°
  10. 10.Two angles of a triangle are 55° and 45°. What is the exterior angle at the third corner? (a) 80° (b) 125° (c) 135° (d) 100°
  11. 11.Two angles of a triangle are 45° and 20°. What is the exterior angle at the third corner? (a) 65° (b) 135° (c) 160° (d) 115°
  12. 12.Two straight lines cross. Two vertically opposite angles add up to 130°. What is each of the other two angles? (a) 50° (b) 115° (c) 65° (d) 230°
  13. 13.Two angles of a triangle are 35° and 80°. What is the third angle? (a) 100° (b) 65° (c) 145° (d) 115°
  14. 14.In an isosceles triangle, the two equal angles are 30° each. What is the third angle? (a) 60° (b) 30° (c) 150° (d) 120°
  15. 15.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) 55° (c) 325° (d) 35°
  16. 16.In an isosceles triangle, the two equal angles are 70° each. What is the third angle? (a) 110° (b) 70° (c) 20° (d) 40°
  17. 17.Two angles of a triangle are 35° and 30°. What is the exterior angle at the third corner? (a) 150° (b) 145° (c) 65° (d) 115°
  18. 18.Two angles of a triangle are 60° and 25°. What is the third angle? (a) 120° (b) 95° (c) 155° (d) 85°
  19. 19.Two straight lines cross. Two vertically opposite angles add up to 240°. What is each of the other two angles? (a) 61° (b) 59° (c) 120° (d) 60°
  20. 20.Two angles of a triangle are 75° and 85°. What is the third angle? (a) 160° (b) 105° (c) 95° (d) 20°
  21. 21.In an isosceles triangle, the two equal angles are 85° each. What is the third angle? (a) 85° (b) 95° (c) 5° (d) 10°
  22. 22.Two angles of a triangle are 30° and 20°. What is the third angle? (a) 150° (b) 130° (c) 160° (d) 50°
  23. 23.Two angles of a triangle are 35° and 75°. What is the third angle? (a) 105° (b) 70° (c) 145° (d) 110°
  24. 24.Two angles of a triangle are 40° and 65°. What is the third angle? (a) 75° (b) 115° (c) 140° (d) 105°
  25. 25.Two straight lines cross. One of the angles is 165°. What is the angle next to it on the same straight line? (a) 15° (b) 195° (c) 165° (d) 16°
  26. 26.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles? (a) 75° (b) 60° (c) 30° (d) 150°
  27. 27.Two angles of a triangle are 55° and 45°. What is the third angle? (a) 125° (b) 80° (c) 100° (d) 135°
  28. 28.Two angles of a triangle are 25° and 65°. What is the third angle? (a) 155° (b) 90° (c) 270° (d) 115°
  29. 29.Two angles of a triangle are 40° and 90°. What is the third angle? (a) 90° (b) 140° (c) 50° (d) 130°
  30. 30.Two angles of a triangle are 30° and 100°. What is the third angle? (a) 80° (b) 150° (c) 130° (d) 50°
  31. 31.Two angles of a triangle are 45° and 70°. What is the third angle? (a) 135° (b) 115° (c) 110° (d) 65°
  32. 32.Two angles of a triangle are 20° and 40°. What is the exterior angle at the third corner? (a) 120° (b) 140° (c) 160° (d) 60°
  33. 33.Two angles of a triangle are 60° and 50°. What is the third angle? (a) 70° (b) 110° (c) 130° (d) 120°
  34. 34.Two angles of a triangle are 55° and 90°. What is the third angle? (a) 125° (b) 35° (c) 90° (d) 145°
  35. 35.Two angles of a triangle are 80° and 45°. What is the third angle? (a) 55° (b) 135° (c) 125° (d) 100°
  36. 36.Two angles of a triangle are 30° and 95°. What is the third angle? (a) 85° (b) 55° (c) 150° (d) 125°
  37. 37.Two angles of a triangle are 55° and 40°. What is the third angle? (a) 125° (b) 140° (c) 95° (d) 85°
  38. 38.Two angles of a triangle are 70° and 45°. What is the third angle? (a) 135° (b) 115° (c) 110° (d) 65°
  39. 39.Two angles of a triangle are 35° and 35°. What is the exterior angle at the third corner? (a) 290° (b) 110° (c) 145° (d) 70°
  40. 40.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°

Answer key

  1. 40°
  2. 55°
  3. 10°
  4. 115°
  5. 70°
  6. 135°
  7. 125°
  8. 85°
  9. 15°
  10. 100°
  11. 65°
  12. 115°
  13. 65°
  14. 120°
  15. 145°
  16. 40°
  17. 65°
  18. 95°
  19. 60°
  20. 20°
  21. 10°
  22. 130°
  23. 70°
  24. 75°
  25. 15°
  26. 75°
  27. 80°
  28. 90°
  29. 50°
  30. 50°
  31. 65°
  32. 60°
  33. 70°
  34. 35°
  35. 55°
  36. 55°
  37. 85°
  38. 65°
  39. 70°
  40. 25°

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