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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 783 · 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.

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  1. 1.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  2. 2.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  3. 3.The two interior opposite angles of a triangle are 76° and 21°. What is the exterior angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  7. 7.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  8. 8.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 77° and angle B = 66°. What is angle C (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 51° and 35°. What is the exterior angle (in degrees)?
  12. 12.In triangle ABC, angle A = 22° and angle B = 71°. What is angle C (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  14. 14.In triangle ABC, angle A = 80° and angle B = 60°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 26° and angle B = 38°. What is angle C (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 24° and 63°. What is the exterior angle (in degrees)?
  17. 17.Can a triangle have sides of 6 cm, 16 cm and 7 cm? (a) Yes (b) No
  18. 18.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 53° and angle B = 31°. What is angle C (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 42° and 51°. What is the exterior angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  22. 22.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  23. 23.Can a triangle have sides of 12 cm, 9 cm and 16 cm? (a) No (b) Yes
  24. 24.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  26. 26.Can a triangle have sides of 11 cm, 11 cm and 2 cm? (a) No (b) Yes
  27. 27.In triangle ABC, angle A = 48° and angle B = 95°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 40° and angle B = 40°. What is angle C (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  30. 30.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  31. 31.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  32. 32.In triangle ABC, angle A = 21° and angle B = 70°. What is angle C (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 7 cm, 4 cm and 10 cm? (a) No (b) Yes
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  36. 36.In triangle ABC, angle A = 32° and angle B = 53°. What is angle C (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 37° and angle B = 72°. What is angle C (in degrees)?
  39. 39.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  40. 40.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?

Answer key

  1. 36
  2. 7
  3. 97
  4. 62
  5. 73
  6. 60
  7. 8
  8. 80
  9. 37
  10. 18
  11. 86
  12. 87
  13. 60
  14. 40
  15. 116
  16. 87
  17. No
  18. 126
  19. 96
  20. 93
  21. 15
  22. 67
  23. Yes
  24. 52
  25. 48
  26. Yes
  27. 37
  28. 100
  29. 39
  30. 48
  31. 53
  32. 89
  33. 68
  34. Yes
  35. 90
  36. 95
  37. 40
  38. 71
  39. 52
  40. 80

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