← Angles and triangles lesson New set →

Angles and Triangles Worksheet for Maths Olympiad

Maths Olympiad topic 21: Angles and triangles · Set 336 · 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 95°. What is the angle next to it on the same straight line? (a) 86° (b) 265° (c) 85° (d) 95°
  2. 2.Two straight lines cross. Two vertically opposite angles add up to 260°. What is each of the other two angles? (a) 51° (b) 50° (c) 130° (d) 100°
  3. 3.Two straight lines cross. Two vertically opposite angles add up to 210°. What is each of the other two angles? (a) 150° (b) 105° (c) 76° (d) 75°
  4. 4.In an isosceles triangle, the two equal angles are 85° each. What is the third angle? (a) 5° (b) 85° (c) 95° (d) 10°
  5. 5.Two angles of a triangle are 50° and 115°. What is the third angle? (a) 165° (b) 65° (c) 15° (d) 130°
  6. 6.Two angles of a triangle are 65° and 65°. What is the third angle? (a) 50° (b) 115° (c) 130° (d) 230°
  7. 7.Two angles of a triangle are 35° and 115°. What is the exterior angle at the third corner? (a) 145° (b) 30° (c) 65° (d) 150°
  8. 8.Two straight lines cross. One of the angles is 35°. What is the angle next to it on the same straight line? (a) 325° (b) 35° (c) 145° (d) 55°
  9. 9.Two straight lines cross. One of the angles is 70°. What is the angle next to it on the same straight line? (a) 290° (b) 20° (c) 110° (d) 70°
  10. 10.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) 30° (d) 60°
  11. 11.Two angles of a triangle are 75° and 25°. What is the exterior angle at the third corner? (a) 80° (b) 105° (c) 100° (d) 155°
  12. 12.Two angles of a triangle are 75° and 60°. What is the third angle? (a) 120° (b) 45° (c) 105° (d) 135°
  13. 13.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) 245° (c) 66° (d) 115°
  14. 14.Two straight lines cross. One of the angles is 105°. What is the angle next to it on the same straight line? (a) 105° (b) 255° (c) 76° (d) 75°
  15. 15.Two angles of a triangle are 20° and 95°. What is the third angle? (a) 115° (b) 85° (c) 160° (d) 65°
  16. 16.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles? (a) 70° (b) 50° (c) 40° (d) 140°
  17. 17.Two straight lines cross. Two vertically opposite angles add up to 120°. What is each of the other two angles? (a) 240° (b) 121° (c) 60° (d) 120°
  18. 18.Two angles of a triangle are 30° and 30°. What is the third angle? (a) 60° (b) 120° (c) 300° (d) 150°
  19. 19.Two angles of a triangle are 25° and 90°. What is the third angle? (a) 115° (b) 155° (c) 65° (d) 90°
  20. 20.Two straight lines cross. One of the angles is 20°. What is the angle next to it on the same straight line? (a) 160° (b) 20° (c) 340° (d) 70°
  21. 21.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles? (a) 100° (b) 40° (c) 50° (d) 80°
  22. 22.Two angles of a triangle are 20° and 55°. What is the exterior angle at the third corner? (a) 160° (b) 105° (c) 125° (d) 75°
  23. 23.Two angles of a triangle are 20° and 115°. What is the third angle? (a) 45° (b) 65° (c) 135° (d) 160°
  24. 24.Two angles of a triangle are 20° and 75°. What is the exterior angle at the third corner? (a) 95° (b) 85° (c) 160° (d) 105°
  25. 25.In an isosceles triangle, the two equal angles are 80° each. What is the third angle? (a) 80° (b) 10° (c) 100° (d) 20°
  26. 26.Two angles of a triangle are 25° and 80°. What is the third angle? (a) 75° (b) 105° (c) 155° (d) 100°
  27. 27.Two angles of a triangle are 70° and 85°. What is the third angle? (a) 110° (b) 25° (c) 155° (d) 95°
  28. 28.Two straight lines cross. Two vertically opposite angles add up to 160°. What is each of the other two angles? (a) 80° (b) 20° (c) 200° (d) 100°
  29. 29.Two angles of a triangle are 35° and 90°. What is the third angle? (a) 90° (b) 125° (c) 145° (d) 55°
  30. 30.Two straight lines cross. One of the angles is 80°. What is the angle next to it on the same straight line? (a) 100° (b) 280° (c) 10° (d) 80°
  31. 31.Two angles of a triangle are 50° and 90°. What is the exterior angle at the third corner? (a) 90° (b) 130° (c) 140° (d) 40°
  32. 32.Two straight lines cross. One of the angles is 155°. What is the angle next to it on the same straight line? (a) 26° (b) 205° (c) 25° (d) 155°
  33. 33.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) 45° (c) 315° (d) 135°
  34. 34.Two angles of a triangle are 40° and 110°. What is the exterior angle at the third corner? (a) 150° (b) 30° (c) 70° (d) 140°
  35. 35.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles? (a) 70° (b) 110° (c) 55° (d) 20°
  36. 36.Two angles of a triangle are 25° and 85°. What is the third angle? (a) 110° (b) 70° (c) 95° (d) 155°
  37. 37.Two angles of a triangle are 25° and 115°. What is the exterior angle at the third corner? (a) 40° (b) 65° (c) 155° (d) 140°
  38. 38.Two angles of a triangle are 35° and 105°. What is the exterior angle at the third corner? (a) 40° (b) 140° (c) 145° (d) 75°
  39. 39.Two straight lines cross. One of the angles is 140°. What is the angle next to it on the same straight line? (a) 140° (b) 41° (c) 220° (d) 40°
  40. 40.In an isosceles triangle, the two equal angles are 50° each. What is the third angle? (a) 80° (b) 130° (c) 40° (d) 50°

Answer key

  1. 85°
  2. 50°
  3. 75°
  4. 10°
  5. 15°
  6. 50°
  7. 150°
  8. 145°
  9. 110°
  10. 30°
  11. 100°
  12. 45°
  13. 65°
  14. 75°
  15. 65°
  16. 70°
  17. 120°
  18. 120°
  19. 65°
  20. 160°
  21. 40°
  22. 75°
  23. 45°
  24. 95°
  25. 20°
  26. 75°
  27. 25°
  28. 100°
  29. 55°
  30. 100°
  31. 140°
  32. 25°
  33. 135°
  34. 150°
  35. 55°
  36. 70°
  37. 140°
  38. 140°
  39. 40°
  40. 80°

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