← Angles and triangles lesson New set →

Angles and Triangles Worksheet for Maths Olympiad

Maths Olympiad topic 21: Angles and triangles · Set 21 · 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 two equal angles are 55° each. What is the third angle? (a) 125° (b) 70° (c) 55° (d) 35°
  2. 2.Two angles of a triangle are 70° and 35°. What is the third angle? (a) 110° (b) 145° (c) 105° (d) 75°
  3. 3.Two straight lines cross. One of the angles is 150°. What is the angle next to it on the same straight line? (a) 150° (b) 210° (c) 31° (d) 30°
  4. 4.Two straight lines cross. One of the angles is 30°. What is the angle next to it on the same straight line? (a) 330° (b) 60° (c) 150° (d) 30°
  5. 5.Two angles of a triangle are 55° and 100°. What is the third angle? (a) 80° (b) 155° (c) 25° (d) 125°
  6. 6.Two angles of a triangle are 50° and 25°. What is the third angle? (a) 75° (b) 105° (c) 130° (d) 155°
  7. 7.Two straight lines cross. Two vertically opposite angles add up to 240°. What is each of the other two angles? (a) 61° (b) 120° (c) 60° (d) 59°
  8. 8.Two straight lines cross. One of the angles is 125°. What is the angle next to it on the same straight line? (a) 125° (b) 235° (c) 55° (d) 56°
  9. 9.Two angles of a triangle are 65° and 35°. What is the third angle? (a) 100° (b) 145° (c) 80° (d) 115°
  10. 10.Two angles of a triangle are 30° and 120°. What is the third angle? (a) 30° (b) 60° (c) 150° (d) 210°
  11. 11.Two angles of a triangle are 40° and 125°. What is the third angle? (a) 55° (b) 140° (c) 15° (d) 165°
  12. 12.In an isosceles triangle, the two equal angles are 50° each. What is the third angle? (a) 130° (b) 40° (c) 50° (d) 80°
  13. 13.Two angles of a triangle are 50° and 80°. What is the exterior angle at the third corner? (a) 230° (b) 50° (c) 100° (d) 130°
  14. 14.Two angles of a triangle are 80° and 85°. What is the third angle? (a) 15° (b) 100° (c) 165° (d) 95°
  15. 15.In an isosceles triangle, the two equal angles are 70° each. What is the third angle? (a) 40° (b) 20° (c) 70° (d) 110°
  16. 16.Two angles of a triangle are 25° and 110°. What is the exterior angle at the third corner? (a) 45° (b) 70° (c) 135° (d) 155°
  17. 17.Two straight lines cross. One of the angles is 165°. What is the angle next to it on the same straight line? (a) 195° (b) 165° (c) 16° (d) 15°
  18. 18.Two straight lines cross. Two vertically opposite angles add up to 230°. What is each of the other two angles? (a) 130° (b) 115° (c) 66° (d) 65°
  19. 19.Two straight lines cross. Two vertically opposite angles add up to 220°. What is each of the other two angles? (a) 140° (b) 70° (c) 110° (d) 71°
  20. 20.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) 80° (d) 10°
  21. 21.Two angles of a triangle are 75° and 60°. What is the third angle? (a) 105° (b) 45° (c) 120° (d) 135°
  22. 22.Two angles of a triangle are 65° and 90°. What is the third angle? (a) 115° (b) 25° (c) 90° (d) 155°
  23. 23.Two angles of a triangle are 40° and 60°. What is the exterior angle at the third corner? (a) 120° (b) 100° (c) 80° (d) 140°
  24. 24.Two angles of a triangle are 60° and 70°. What is the third angle? (a) 110° (b) 50° (c) 120° (d) 130°
  25. 25.Two angles of a triangle are 65° and 60°. What is the third angle? (a) 115° (b) 55° (c) 120° (d) 125°
  26. 26.Two angles of a triangle are 65° and 50°. What is the third angle? (a) 115° (b) 245° (c) 130° (d) 65°
  27. 27.In an isosceles triangle, the two equal angles are 45° each. What is the third angle? (a) 45° (b) 135° (c) 90° (d) 91°
  28. 28.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles? (a) 46° (b) 45° (c) 90° (d) 55°
  29. 29.Two angles of a triangle are 25° and 50°. What is the exterior angle at the third corner? (a) 105° (b) 75° (c) 130° (d) 155°
  30. 30.Two angles of a triangle are 50° and 55°. What is the exterior angle at the third corner? (a) 105° (b) 75° (c) 130° (d) 125°
  31. 31.Two angles of a triangle are 50° and 95°. What is the exterior angle at the third corner? (a) 145° (b) 130° (c) 85° (d) 35°
  32. 32.Two angles of a triangle are 50° and 80°. What is the third angle? (a) 50° (b) 230° (c) 100° (d) 130°
  33. 33.Two angles of a triangle are 45° and 95°. What is the third angle? (a) 140° (b) 135° (c) 85° (d) 40°
  34. 34.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles? (a) 20° (b) 40° (c) 30° (d) 140°
  35. 35.Two angles of a triangle are 20° and 65°. What is the exterior angle at the third corner? (a) 160° (b) 115° (c) 95° (d) 85°
  36. 36.Two angles of a triangle are 35° and 100°. What is the third angle? (a) 145° (b) 135° (c) 80° (d) 45°
  37. 37.Two angles of a triangle are 80° and 90°. What is the third angle? (a) 10° (b) 170° (c) 90° (d) 100°
  38. 38.Two angles of a triangle are 30° and 60°. What is the exterior angle at the third corner? (a) 90° (b) 120° (c) 270° (d) 150°
  39. 39.Two straight lines cross. One of the angles is 170°. What is the angle next to it on the same straight line? (a) 11° (b) 10° (c) 190° (d) 170°
  40. 40.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles? (a) 50° (b) 100° (c) 40° (d) 80°

Answer key

  1. 70°
  2. 75°
  3. 30°
  4. 150°
  5. 25°
  6. 105°
  7. 60°
  8. 55°
  9. 80°
  10. 30°
  11. 15°
  12. 80°
  13. 130°
  14. 15°
  15. 40°
  16. 135°
  17. 15°
  18. 65°
  19. 70°
  20. 100°
  21. 45°
  22. 25°
  23. 100°
  24. 50°
  25. 55°
  26. 65°
  27. 90°
  28. 45°
  29. 75°
  30. 105°
  31. 145°
  32. 50°
  33. 40°
  34. 20°
  35. 85°
  36. 45°
  37. 10°
  38. 90°
  39. 10°
  40. 40°

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