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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 81 · 40 sums
TalentJR

The method (Inside 180, outside the sum): Angle sum: ∠A + ∠B + ∠C = 180°. Exterior angle = sum of the two interior opposite angles. Right-angled triangle: longest side² = side² + side² (3, 4, 5 and 5, 12, 13 are famous sets). Sides can make a triangle only if the two shorter sides add up to more than the longest side.

NameDateTime takenScore ___ / 40
  1. 1.The two interior opposite angles of a triangle are 64° and 43°. What is the exterior angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 36° and 72°. What is the exterior angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 20° and angle B = 96°. What is angle C (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  6. 6.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  7. 7.In triangle ABC, angle A = 42° and angle B = 80°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 78° and angle B = 64°. What is angle C (in degrees)?
  9. 9.Can a triangle have sides of 12 cm, 6 cm and 3 cm? (a) Yes (b) No
  10. 10.In triangle ABC, angle A = 81° and angle B = 43°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 36° and 73°. What is the exterior angle (in degrees)?
  13. 13.Can a triangle have sides of 8 cm, 17 cm and 7 cm? (a) Yes (b) No
  14. 14.Can a triangle have sides of 21 cm, 12 cm and 5 cm? (a) Yes (b) No
  15. 15.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  16. 16.An exterior angle of a triangle is 52°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  17. 17.In triangle ABC, angle A = 76° and angle B = 29°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 50° and 49°. What is the exterior angle (in degrees)?
  21. 21.In triangle ABC, angle A = 39° and angle B = 92°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 8 cm, 6 cm and 3 cm? (a) Yes (b) No
  23. 23.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  26. 26.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  27. 27.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  28. 28.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  30. 30.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 4 cm, 8 cm and 10 cm? (a) No (b) Yes
  33. 33.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  35. 35.In triangle ABC, angle A = 76° and angle B = 28°. What is angle C (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 77° and angle B = 64°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  39. 39.Can a triangle have sides of 10 cm, 14 cm and 7 cm? (a) No (b) Yes
  40. 40.In triangle ABC, angle A = 96° and angle B = 47°. What is angle C (in degrees)?

Answer key

  1. 107
  2. 108
  3. 18
  4. 64
  5. 77
  6. 30
  7. 58
  8. 38
  9. No
  10. 56
  11. 35
  12. 109
  13. No
  14. No
  15. 75
  16. 27
  17. 75
  18. 47
  19. 56
  20. 99
  21. 49
  22. Yes
  23. 20
  24. 32
  25. 64
  26. 12
  27. 26
  28. 19
  29. 25
  30. 65
  31. 73
  32. Yes
  33. 79
  34. 75
  35. 76
  36. 53
  37. 39
  38. 70
  39. Yes
  40. 37

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