← Angles and triangles lesson New set →

Angles and Triangles Worksheet for Maths Olympiad

Maths Olympiad topic 21: Angles and triangles · Set 140 · 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 45° and 50°. What is the exterior angle at the third corner? (a) 135° (b) 85° (c) 130° (d) 95°
  2. 2.Two angles of a triangle are 35° and 85°. What is the exterior angle at the third corner? (a) 95° (b) 145° (c) 120° (d) 60°
  3. 3.Two angles of a triangle are 25° and 30°. What is the exterior angle at the third corner? (a) 125° (b) 55° (c) 155° (d) 150°
  4. 4.Two angles of a triangle are 35° and 30°. What is the third angle? (a) 115° (b) 65° (c) 145° (d) 150°
  5. 5.Two angles of a triangle are 20° and 65°. What is the exterior angle at the third corner? (a) 160° (b) 115° (c) 85° (d) 95°
  6. 6.Two straight lines cross. Two vertically opposite angles add up to 280°. What is each of the other two angles? (a) 140° (b) 80° (c) 41° (d) 40°
  7. 7.In an isosceles triangle, the two equal angles are 25° each. What is the third angle? (a) 65° (b) 155° (c) 25° (d) 130°
  8. 8.Two angles of a triangle are 70° and 40°. What is the third angle? (a) 70° (b) 140° (c) 110° (d) 250°
  9. 9.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles? (a) 50° (b) 40° (c) 130° (d) 65°
  10. 10.Two angles of a triangle are 70° and 90°. What is the third angle? (a) 110° (b) 160° (c) 90° (d) 20°
  11. 11.Two angles of a triangle are 65° and 20°. What is the exterior angle at the third corner? (a) 95° (b) 85° (c) 160° (d) 115°
  12. 12.Two angles of a triangle are 40° and 50°. What is the third angle? (a) 130° (b) 90° (c) 270° (d) 140°
  13. 13.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles? (a) 70° (b) 40° (c) 50° (d) 140°
  14. 14.Two angles of a triangle are 35° and 130°. What is the third angle? (a) 50° (b) 145° (c) 15° (d) 165°
  15. 15.Two straight lines cross. Two vertically opposite angles add up to 200°. What is each of the other two angles? (a) 81° (b) 80° (c) 160° (d) 100°
  16. 16.In an isosceles triangle, the two equal angles are 40° each. What is the third angle? (a) 50° (b) 40° (c) 100° (d) 140°
  17. 17.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles? (a) 20° (b) 160° (c) 11° (d) 10°
  18. 18.Two angles of a triangle are 70° and 75°. What is the exterior angle at the third corner? (a) 105° (b) 35° (c) 145° (d) 110°
  19. 19.Two angles of a triangle are 30° and 115°. What is the exterior angle at the third corner? (a) 145° (b) 150° (c) 35° (d) 65°
  20. 20.Two straight lines cross. Two vertically opposite angles add up to 290°. What is each of the other two angles? (a) 145° (b) 36° (c) 70° (d) 35°
  21. 21.Two straight lines cross. Two vertically opposite angles add up to 310°. What is each of the other two angles? (a) 155° (b) 25° (c) 26° (d) 50°
  22. 22.Two angles of a triangle are 35° and 100°. What is the third angle? (a) 45° (b) 145° (c) 80° (d) 135°
  23. 23.Two angles of a triangle are 50° and 80°. What is the third angle? (a) 230° (b) 130° (c) 100° (d) 50°
  24. 24.Two angles of a triangle are 40° and 80°. What is the exterior angle at the third corner? (a) 140° (b) 100° (c) 60° (d) 120°
  25. 25.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles? (a) 110° (b) 70° (c) 55° (d) 20°
  26. 26.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles? (a) 70° (b) 80° (c) 20° (d) 160°
  27. 27.Two angles of a triangle are 35° and 125°. What is the third angle? (a) 20° (b) 55° (c) 145° (d) 160°
  28. 28.Two angles of a triangle are 50° and 40°. What is the exterior angle at the third corner? (a) 140° (b) 270° (c) 130° (d) 90°
  29. 29.Two angles of a triangle are 70° and 20°. What is the exterior angle at the third corner? (a) 160° (b) 110° (c) 270° (d) 90°
  30. 30.Two angles of a triangle are 25° and 110°. What is the exterior angle at the third corner? (a) 155° (b) 70° (c) 135° (d) 45°
  31. 31.Two straight lines cross. Two vertically opposite angles add up to 90°. What is each of the other two angles? (a) 90° (b) 270° (c) 135° (d) 45°
  32. 32.Two straight lines cross. One of the angles is 85°. What is the angle next to it on the same straight line? (a) 5° (b) 275° (c) 95° (d) 85°
  33. 33.Two straight lines cross. Two vertically opposite angles add up to 260°. What is each of the other two angles? (a) 50° (b) 130° (c) 51° (d) 100°
  34. 34.Two angles of a triangle are 45° and 20°. What is the exterior angle at the third corner? (a) 115° (b) 160° (c) 65° (d) 135°
  35. 35.Two angles of a triangle are 80° and 35°. What is the third angle? (a) 145° (b) 115° (c) 100° (d) 65°
  36. 36.Two angles of a triangle are 25° and 60°. What is the exterior angle at the third corner? (a) 155° (b) 120° (c) 95° (d) 85°
  37. 37.In an isosceles triangle, the two equal angles are 60° each. What is the third angle? (a) 60° (b) 30° (c) 61° (d) 120°
  38. 38.Two angles of a triangle are 40° and 40°. What is the exterior angle at the third corner? (a) 80° (b) 280° (c) 100° (d) 140°
  39. 39.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles? (a) 40° (b) 30° (c) 120° (d) 60°
  40. 40.Two angles of a triangle are 45° and 30°. What is the third angle? (a) 135° (b) 105° (c) 75° (d) 150°

Answer key

  1. 95°
  2. 120°
  3. 55°
  4. 115°
  5. 85°
  6. 40°
  7. 130°
  8. 70°
  9. 65°
  10. 20°
  11. 85°
  12. 90°
  13. 70°
  14. 15°
  15. 80°
  16. 100°
  17. 10°
  18. 145°
  19. 145°
  20. 35°
  21. 25°
  22. 45°
  23. 50°
  24. 120°
  25. 55°
  26. 80°
  27. 20°
  28. 90°
  29. 90°
  30. 135°
  31. 135°
  32. 95°
  33. 50°
  34. 65°
  35. 65°
  36. 85°
  37. 60°
  38. 80°
  39. 30°
  40. 105°

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