← Angles and triangles lesson New set →

Angles and Triangles Worksheet for Maths Olympiad

Maths Olympiad topic 21: Angles and triangles · Set 62 · 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) 85° (b) 265° (c) 95° (d) 86°
  2. 2.Two angles of a triangle are 20° and 100°. What is the third angle? (a) 160° (b) 120° (c) 80° (d) 60°
  3. 3.Two angles of a triangle are 45° and 65°. What is the third angle? (a) 110° (b) 115° (c) 70° (d) 135°
  4. 4.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles? (a) 45° (b) 55° (c) 90° (d) 46°
  5. 5.Two straight lines cross. One of the angles is 160°. What is the angle next to it on the same straight line? (a) 200° (b) 21° (c) 20° (d) 160°
  6. 6.Two angles of a triangle are 60° and 85°. What is the third angle? (a) 120° (b) 145° (c) 35° (d) 95°
  7. 7.Two angles of a triangle are 60° and 60°. What is the third angle? (a) 61° (b) 240° (c) 120° (d) 60°
  8. 8.In an isosceles triangle, the two equal angles are 85° each. What is the third angle? (a) 10° (b) 95° (c) 85° (d) 5°
  9. 9.Two angles of a triangle are 55° and 70°. What is the third angle? (a) 235° (b) 110° (c) 55° (d) 125°
  10. 10.Two angles of a triangle are 25° and 75°. What is the exterior angle at the third corner? (a) 100° (b) 155° (c) 105° (d) 80°
  11. 11.Two angles of a triangle are 65° and 95°. What is the third angle? (a) 160° (b) 115° (c) 85° (d) 20°
  12. 12.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles? (a) 100° (b) 10° (c) 80° (d) 50°
  13. 13.Two angles of a triangle are 35° and 45°. What is the third angle? (a) 100° (b) 80° (c) 145° (d) 135°
  14. 14.Two angles of a triangle are 60° and 30°. What is the exterior angle at the third corner? (a) 120° (b) 270° (c) 150° (d) 90°
  15. 15.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles? (a) 160° (b) 20° (c) 70° (d) 80°
  16. 16.Two angles of a triangle are 50° and 30°. What is the exterior angle at the third corner? (a) 130° (b) 150° (c) 100° (d) 80°
  17. 17.Two angles of a triangle are 75° and 45°. What is the third angle? (a) 120° (b) 60° (c) 105° (d) 135°
  18. 18.In an isosceles triangle, the two equal angles are 40° each. What is the third angle? (a) 100° (b) 140° (c) 50° (d) 40°
  19. 19.Two straight lines cross. One of the angles is 75°. What is the angle next to it on the same straight line? (a) 75° (b) 105° (c) 285° (d) 15°
  20. 20.Two straight lines cross. Two vertically opposite angles add up to 330°. What is each of the other two angles? (a) 16° (b) 165° (c) 15° (d) 30°
  21. 21.Two angles of a triangle are 70° and 25°. What is the exterior angle at the third corner? (a) 155° (b) 110° (c) 95° (d) 85°
  22. 22.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°
  23. 23.In an isosceles triangle, the two equal angles are 75° each. What is the third angle? (a) 15° (b) 75° (c) 105° (d) 30°
  24. 24.Two angles of a triangle are 70° and 40°. What is the exterior angle at the third corner? (a) 110° (b) 70° (c) 250° (d) 140°
  25. 25.In an isosceles triangle, the two equal angles are 30° each. What is the third angle? (a) 30° (b) 60° (c) 120° (d) 150°
  26. 26.Two straight lines cross. One of the angles is 145°. What is the angle next to it on the same straight line? (a) 215° (b) 36° (c) 35° (d) 145°
  27. 27.In an isosceles triangle, the two equal angles are 80° each. What is the third angle? (a) 100° (b) 20° (c) 10° (d) 80°
  28. 28.Two straight lines cross. One of the angles is 65°. What is the angle next to it on the same straight line? (a) 295° (b) 25° (c) 115° (d) 65°
  29. 29.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°
  30. 30.Two angles of a triangle are 75° and 25°. What is the exterior angle at the third corner? (a) 155° (b) 80° (c) 105° (d) 100°
  31. 31.Two straight lines cross. One of the angles is 20°. What is the angle next to it on the same straight line? (a) 20° (b) 70° (c) 340° (d) 160°
  32. 32.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles? (a) 75° (b) 150° (c) 60° (d) 30°
  33. 33.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles? (a) 130° (b) 50° (c) 65° (d) 40°
  34. 34.Two angles of a triangle are 25° and 125°. What is the exterior angle at the third corner? (a) 150° (b) 155° (c) 30° (d) 55°
  35. 35.Two angles of a triangle are 45° and 30°. What is the third angle? (a) 150° (b) 75° (c) 105° (d) 135°
  36. 36.In an isosceles triangle, the two equal angles are 35° each. What is the third angle? (a) 110° (b) 55° (c) 145° (d) 35°
  37. 37.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles? (a) 20° (b) 55° (c) 70° (d) 110°
  38. 38.Two angles of a triangle are 80° and 20°. What is the third angle? (a) 80° (b) 260° (c) 100° (d) 160°
  39. 39.Two straight lines cross. Two vertically opposite angles add up to 190°. What is each of the other two angles? (a) 86° (b) 170° (c) 95° (d) 85°
  40. 40.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles? (a) 40° (b) 30° (c) 140° (d) 20°

Answer key

  1. 85°
  2. 60°
  3. 70°
  4. 45°
  5. 20°
  6. 35°
  7. 60°
  8. 10°
  9. 55°
  10. 100°
  11. 20°
  12. 50°
  13. 100°
  14. 90°
  15. 80°
  16. 80°
  17. 60°
  18. 100°
  19. 105°
  20. 15°
  21. 95°
  22. 40°
  23. 30°
  24. 110°
  25. 120°
  26. 35°
  27. 20°
  28. 115°
  29. 10°
  30. 100°
  31. 160°
  32. 75°
  33. 65°
  34. 150°
  35. 105°
  36. 110°
  37. 55°
  38. 80°
  39. 85°
  40. 20°

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