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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 746 · 40 sums
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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.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  7. 7.Can a triangle have sides of 2 cm, 3 cm and 9 cm? (a) No (b) Yes
  8. 8.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  9. 9.The two interior opposite angles of a triangle are 77° and 24°. What is the exterior angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 31° and angle B = 37°. What is angle C (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 29° and 58°. What is the exterior angle (in degrees)?
  13. 13.Can a triangle have sides of 4 cm, 14 cm and 10 cm? (a) Yes (b) No
  14. 14.In triangle ABC, angle A = 94° and angle B = 32°. What is angle C (in degrees)?
  15. 15.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  18. 18.Can a triangle have sides of 11 cm, 12 cm and 2 cm? (a) No (b) Yes
  19. 19.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  20. 20.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  21. 21.In triangle ABC, angle A = 43° and angle B = 22°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 74° and angle B = 51°. What is angle C (in degrees)?
  23. 23.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)?
  24. 24.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  26. 26.Can a triangle have sides of 9 cm, 18 cm and 4 cm? (a) No (b) Yes
  27. 27.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 26° and 26°. What is the exterior angle (in degrees)?
  29. 29.In triangle ABC, angle A = 61° and angle B = 52°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 8 cm, 4 cm and 13 cm? (a) Yes (b) No
  31. 31.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 7 cm, 7 cm and 3 cm? (a) No (b) Yes
  33. 33.In triangle ABC, angle A = 25° and angle B = 130°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 11 cm, 8 cm and 4 cm? (a) Yes (b) No
  35. 35.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  37. 37.In triangle ABC, angle A = 75° and angle B = 40°. What is angle C (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  39. 39.Can a triangle have sides of 11 cm, 15 cm and 2 cm? (a) Yes (b) No
  40. 40.In an isosceles triangle, the angle between the two equal sides is 104°. What is each of the other two angles (in degrees)?

Answer key

  1. 62
  2. 84
  3. 72
  4. 15
  5. 11
  6. 90
  7. No
  8. 26
  9. 101
  10. 69
  11. 112
  12. 87
  13. No
  14. 54
  15. 72
  16. 15
  17. 60
  18. Yes
  19. 15
  20. 27
  21. 115
  22. 55
  23. 8
  24. 47
  25. 36
  26. No
  27. 66
  28. 52
  29. 67
  30. No
  31. 49
  32. Yes
  33. 25
  34. Yes
  35. 48
  36. 90
  37. 65
  38. 30
  39. No
  40. 38

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