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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 131 · 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 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  2. 2.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 23° and 21°. What is the exterior angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 79° and 43°. What is the exterior angle (in degrees)?
  5. 5.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  6. 6.In triangle ABC, angle A = 30° and angle B = 31°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 90° and angle B = 27°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 43° and angle B = 94°. What is angle C (in degrees)?
  9. 9.Can a triangle have sides of 17 cm, 8 cm and 8 cm? (a) No (b) Yes
  10. 10.Can a triangle have sides of 2 cm, 8 cm and 8 cm? (a) No (b) Yes
  11. 11.In triangle ABC, angle A = 44° and angle B = 89°. What is angle C (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 34° and 61°. What is the exterior angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 62° and 64°. What is the exterior angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 33° and angle B = 76°. What is angle C (in degrees)?
  19. 19.Can a triangle have sides of 6 cm, 20 cm and 12 cm? (a) No (b) Yes
  20. 20.In triangle ABC, angle A = 72° and angle B = 83°. What is angle C (in degrees)?
  21. 21.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  22. 22.In triangle ABC, angle A = 86° and angle B = 63°. What is angle C (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 29° and angle B = 21°. What is angle C (in degrees)?
  27. 27.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  28. 28.In triangle ABC, angle A = 28° and angle B = 84°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 42° and 46°. What is the exterior angle (in degrees)?
  31. 31.An exterior angle of a triangle is 126°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  32. 32.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  33. 33.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  35. 35.Can a triangle have sides of 4 cm, 2 cm and 9 cm? (a) Yes (b) No
  36. 36.In triangle ABC, angle A = 84° and angle B = 55°. What is angle C (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 26° and 43°. What is the exterior angle (in degrees)?
  38. 38.Can a triangle have sides of 11 cm, 12 cm and 3 cm? (a) Yes (b) No
  39. 39.In triangle ABC, angle A = 96° and angle B = 27°. What is angle C (in degrees)?
  40. 40.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?

Answer key

  1. 24
  2. 90
  3. 44
  4. 122
  5. 12
  6. 119
  7. 63
  8. 43
  9. No
  10. Yes
  11. 47
  12. 95
  13. 30
  14. 72
  15. 126
  16. 62
  17. 108
  18. 71
  19. No
  20. 25
  21. 10
  22. 31
  23. 84
  24. 27
  25. 42
  26. 130
  27. 59
  28. 68
  29. 66
  30. 88
  31. 52
  32. 24
  33. 58
  34. 70
  35. No
  36. 41
  37. 69
  38. Yes
  39. 57
  40. 8

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