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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 740 · 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 triangle ABC, angle A = 62° and angle B = 43°. What is angle C (in degrees)?
  2. 2.An exterior angle of a triangle is 57°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  5. 5.In triangle ABC, angle A = 64° and angle B = 62°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  8. 8.The two interior opposite angles of a triangle are 54° and 60°. What is the exterior angle (in degrees)?
  9. 9.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)?
  10. 10.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 34° and 33°. What is the exterior angle (in degrees)?
  14. 14.Can a triangle have sides of 11 cm, 3 cm and 12 cm? (a) No (b) Yes
  15. 15.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  16. 16.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 75° and angle B = 83°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 64°. What is each of the other two angles (in degrees)?
  21. 21.In triangle ABC, angle A = 80° and angle B = 42°. What is angle C (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  25. 25.In triangle ABC, angle A = 88° and angle B = 20°. What is angle C (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 21° and 56°. What is the exterior angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  28. 28.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 45° and 25°. What is the exterior angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 27° and 21°. What is the exterior angle (in degrees)?
  31. 31.In triangle ABC, angle A = 67° and angle B = 33°. What is angle C (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  33. 33.An exterior angle of a triangle is 159°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  35. 35.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  36. 36.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  37. 37.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 74° and 32°. What is the exterior angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?

Answer key

  1. 75
  2. 21
  3. 40
  4. 19
  5. 54
  6. 25
  7. 17
  8. 114
  9. 15
  10. 26
  11. 53
  12. 82
  13. 67
  14. Yes
  15. 17
  16. 30
  17. 120
  18. 55
  19. 22
  20. 58
  21. 58
  22. 28
  23. 31
  24. 25
  25. 72
  26. 77
  27. 66
  28. 21
  29. 70
  30. 48
  31. 80
  32. 65
  33. 79
  34. 80
  35. 20
  36. 25
  37. 44
  38. 50
  39. 106
  40. 67

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