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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 824 · 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.In triangle ABC, angle A = 57° and angle B = 21°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 12 cm, 12 cm and 3 cm? (a) No (b) Yes
  3. 3.In triangle ABC, angle A = 79° and angle B = 24°. What is angle C (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 8 cm, 1 cm and 8 cm? (a) Yes (b) No
  7. 7.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 12 cm, 8 cm and 10 cm? (a) No (b) Yes
  9. 9.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  11. 11.In triangle ABC, angle A = 67° and angle B = 37°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 24° and angle B = 60°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 74° and angle B = 65°. What is angle C (in degrees)?
  14. 14.Can a triangle have sides of 18 cm, 3 cm and 12 cm? (a) Yes (b) No
  15. 15.The two interior opposite angles of a triangle are 74° and 62°. What is the exterior angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 76° and angle B = 51°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 19 cm, 7 cm and 12 cm? (a) Yes (b) No
  20. 20.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  22. 22.The two interior opposite angles of a triangle are 50° and 60°. What is the exterior angle (in degrees)?
  23. 23.In triangle ABC, angle A = 78° and angle B = 21°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 94° and angle B = 58°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  27. 27.In triangle ABC, angle A = 44° and angle B = 50°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 9 cm, 5 cm and 12 cm? (a) Yes (b) No
  29. 29.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  30. 30.In triangle ABC, angle A = 21° and angle B = 128°. What is angle C (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 58° and 30°. What is the exterior angle (in degrees)?
  35. 35.In triangle ABC, angle A = 22° and angle B = 40°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 84° and angle B = 25°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  39. 39.In triangle ABC, angle A = 95° and angle B = 39°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 11 cm, 2 cm and 9 cm? (a) No (b) Yes

Answer key

  1. 102
  2. Yes
  3. 77
  4. 25
  5. 90
  6. Yes
  7. 61
  8. Yes
  9. 60
  10. 15
  11. 76
  12. 96
  13. 41
  14. No
  15. 136
  16. 90
  17. 53
  18. 20
  19. No
  20. 18
  21. 25
  22. 110
  23. 81
  24. 71
  25. 28
  26. 50
  27. 86
  28. Yes
  29. 84
  30. 31
  31. 16
  32. 80
  33. 31
  34. 88
  35. 118
  36. 71
  37. 53
  38. 75
  39. 46
  40. No

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