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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 682 · 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.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  2. 2.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 32° and angle B = 51°. What is angle C (in degrees)?
  4. 4.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 53°. What is the other one (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 = 41° and angle B = 83°. What is angle C (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 51° and 62°. What is the exterior angle (in degrees)?
  8. 8.In triangle ABC, angle A = 57° and angle B = 85°. What is angle C (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  10. 10.The two interior opposite angles of a triangle are 55° and 64°. What is the exterior angle (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  12. 12.In triangle ABC, angle A = 66° and angle B = 53°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 74° and angle B = 28°. What is angle C (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 5 cm, 6 cm and 2 cm? (a) No (b) Yes
  22. 22.An exterior angle of a triangle is 54°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  23. 23.In triangle ABC, angle A = 86° and angle B = 23°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  27. 27.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  28. 28.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  29. 29.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  30. 30.In triangle ABC, angle A = 26° and angle B = 41°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 89° and angle B = 65°. What is angle C (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  33. 33.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  36. 36.Can a triangle have sides of 12 cm, 5 cm and 10 cm? (a) Yes (b) No
  37. 37.In triangle ABC, angle A = 58° and angle B = 28°. What is angle C (in degrees)?
  38. 38.In triangle ABC, angle A = 24° and angle B = 90°. What is angle C (in degrees)?
  39. 39.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  40. 40.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?

Answer key

  1. 25
  2. 64
  3. 97
  4. 30
  5. 12
  6. 56
  7. 113
  8. 38
  9. 20
  10. 119
  11. 17
  12. 61
  13. 69
  14. 38
  15. 100
  16. 60
  17. 100
  18. 31
  19. 78
  20. 49
  21. Yes
  22. 30
  23. 71
  24. 47
  25. 132
  26. 80
  27. 48
  28. 37
  29. 28
  30. 113
  31. 26
  32. 40
  33. 35
  34. 19
  35. 17
  36. Yes
  37. 94
  38. 66
  39. 41
  40. 15

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