← Angles and triangles lesson New set →

Angles and Triangles Worksheet for Maths Olympiad

Maths Olympiad topic 21: Angles and triangles · Set 381 · 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 80° and 65°. What is the third angle? (a) 145° (b) 115° (c) 100° (d) 35°
  2. 2.Two angles of a triangle are 70° and 50°. What is the third angle? (a) 120° (b) 60° (c) 110° (d) 130°
  3. 3.Two angles of a triangle are 75° and 60°. What is the exterior angle at the third corner? (a) 135° (b) 120° (c) 45° (d) 105°
  4. 4.Two straight lines cross. One of the angles is 145°. What is the angle next to it on the same straight line? (a) 35° (b) 36° (c) 145° (d) 215°
  5. 5.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) 40° (d) 65°
  6. 6.Two angles of a triangle are 70° and 65°. What is the exterior angle at the third corner? (a) 110° (b) 115° (c) 45° (d) 135°
  7. 7.Two angles of a triangle are 45° and 35°. What is the third angle? (a) 135° (b) 100° (c) 80° (d) 145°
  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) 145° (b) 35° (c) 325° (d) 55°
  9. 9.Two angles of a triangle are 55° and 80°. What is the third angle? (a) 125° (b) 135° (c) 100° (d) 45°
  10. 10.Two angles of a triangle are 40° and 55°. What is the exterior angle at the third corner? (a) 140° (b) 85° (c) 125° (d) 95°
  11. 11.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles? (a) 160° (b) 10° (c) 11° (d) 20°
  12. 12.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles? (a) 20° (b) 30° (c) 40° (d) 140°
  13. 13.In an isosceles triangle, the two equal angles are 75° each. What is the third angle? (a) 105° (b) 15° (c) 75° (d) 30°
  14. 14.In an isosceles triangle, the two equal angles are 25° each. What is the third angle? (a) 130° (b) 25° (c) 155° (d) 65°
  15. 15.In an isosceles triangle, the two equal angles are 40° each. What is the third angle? (a) 50° (b) 40° (c) 140° (d) 100°
  16. 16.Two straight lines cross. One of the angles is 120°. What is the angle next to it on the same straight line? (a) 61° (b) 60° (c) 240° (d) 120°
  17. 17.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles? (a) 40° (b) 70° (c) 140° (d) 50°
  18. 18.Two angles of a triangle are 45° and 50°. What is the third angle? (a) 130° (b) 135° (c) 85° (d) 95°
  19. 19.Two angles of a triangle are 25° and 95°. What is the third angle? (a) 120° (b) 155° (c) 60° (d) 85°
  20. 20.Two angles of a triangle are 30° and 55°. What is the third angle? (a) 150° (b) 95° (c) 85° (d) 125°
  21. 21.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles? (a) 20° (b) 80° (c) 70° (d) 160°
  22. 22.Two straight lines cross. Two vertically opposite angles add up to 190°. What is each of the other two angles? (a) 170° (b) 95° (c) 86° (d) 85°
  23. 23.Two angles of a triangle are 75° and 95°. What is the third angle? (a) 105° (b) 10° (c) 85° (d) 170°
  24. 24.Two angles of a triangle are 50° and 70°. What is the exterior angle at the third corner? (a) 130° (b) 110° (c) 120° (d) 60°
  25. 25.Two straight lines cross. Two vertically opposite angles add up to 240°. What is each of the other two angles? (a) 120° (b) 61° (c) 59° (d) 60°
  26. 26.Two angles of a triangle are 50° and 35°. What is the third angle? (a) 130° (b) 95° (c) 145° (d) 85°
  27. 27.Two straight lines cross. Two vertically opposite angles add up to 270°. What is each of the other two angles? (a) 135° (b) 90° (c) 45° (d) 46°
  28. 28.Two straight lines cross. Two vertically opposite angles add up to 330°. What is each of the other two angles? (a) 16° (b) 15° (c) 165° (d) 30°
  29. 29.Two straight lines cross. Two vertically opposite angles add up to 120°. What is each of the other two angles? (a) 120° (b) 240° (c) 60° (d) 121°
  30. 30.Two angles of a triangle are 20° and 80°. What is the exterior angle at the third corner? (a) 80° (b) 160° (c) 260° (d) 100°
  31. 31.Two angles of a triangle are 65° and 50°. What is the third angle? (a) 115° (b) 130° (c) 65° (d) 245°
  32. 32.In an isosceles triangle, the two equal angles are 45° each. What is the third angle? (a) 90° (b) 91° (c) 45° (d) 135°
  33. 33.Two angles of a triangle are 20° and 80°. What is the third angle? (a) 260° (b) 80° (c) 100° (d) 160°
  34. 34.Two angles of a triangle are 45° and 20°. What is the third angle? (a) 115° (b) 135° (c) 160° (d) 65°
  35. 35.Two angles of a triangle are 60° and 85°. What is the third angle? (a) 145° (b) 35° (c) 95° (d) 120°
  36. 36.Two straight lines cross. Two vertically opposite angles add up to 230°. What is each of the other two angles? (a) 65° (b) 115° (c) 130° (d) 66°
  37. 37.In an isosceles triangle, the two equal angles are 60° each. What is the third angle? (a) 61° (b) 60° (c) 30° (d) 120°
  38. 38.Two angles of a triangle are 80° and 80°. What is the third angle? (a) 200° (b) 100° (c) 160° (d) 20°
  39. 39.Two angles of a triangle are 25° and 40°. What is the exterior angle at the third corner? (a) 140° (b) 155° (c) 65° (d) 115°
  40. 40.Two straight lines cross. Two vertically opposite angles add up to 200°. What is each of the other two angles? (a) 100° (b) 160° (c) 81° (d) 80°

Answer key

  1. 35°
  2. 60°
  3. 135°
  4. 35°
  5. 65°
  6. 135°
  7. 100°
  8. 145°
  9. 45°
  10. 95°
  11. 10°
  12. 20°
  13. 30°
  14. 130°
  15. 100°
  16. 60°
  17. 70°
  18. 85°
  19. 60°
  20. 95°
  21. 80°
  22. 85°
  23. 10°
  24. 120°
  25. 60°
  26. 95°
  27. 45°
  28. 15°
  29. 120°
  30. 100°
  31. 65°
  32. 90°
  33. 80°
  34. 115°
  35. 35°
  36. 65°
  37. 60°
  38. 20°
  39. 65°
  40. 80°

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