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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 958 · 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.

NameDateTime takenScore ___ / 40
  1. 1.Can a triangle have sides of 12 cm, 2 cm and 13 cm? (a) No (b) Yes
  2. 2.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  3. 3.In triangle ABC, angle A = 88° and angle B = 33°. What is angle C (in degrees)?
  4. 4.In triangle ABC, angle A = 78° and angle B = 20°. What is angle C (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 48° and 58°. What is the exterior angle (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 9 cm, 11 cm and 7 cm? (a) No (b) Yes
  9. 9.In triangle ABC, angle A = 55° and angle B = 98°. What is angle C (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 112°. What is each of the other two angles (in degrees)?
  12. 12.Can a triangle have sides of 14 cm, 4 cm and 9 cm? (a) No (b) Yes
  13. 13.In triangle ABC, angle A = 62° and angle B = 81°. What is angle C (in degrees)?
  14. 14.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  17. 17.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)?
  18. 18.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 24° and 55°. What is the exterior angle (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  25. 25.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  26. 26.In triangle ABC, angle A = 58° and angle B = 87°. What is angle C (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 96° and angle B = 39°. What is angle C (in degrees)?
  32. 32.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  33. 33.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  34. 34.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  36. 36.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  38. 38.In triangle ABC, angle A = 34° and angle B = 103°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 40° and angle B = 84°. What is angle C (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?

Answer key

  1. Yes
  2. 72
  3. 59
  4. 82
  5. 106
  6. 36
  7. 28
  8. Yes
  9. 27
  10. 90
  11. 34
  12. No
  13. 37
  14. 52
  15. 80
  16. 90
  17. 10
  18. 100
  19. 20
  20. 79
  21. 70
  22. 70
  23. 136
  24. 67
  25. 51
  26. 35
  27. 90
  28. 33
  29. 50
  30. 22
  31. 45
  32. 16
  33. 72
  34. 46
  35. 13
  36. 16
  37. 15
  38. 43
  39. 56
  40. 25

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