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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 927 · 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 15 cm and 36 cm. How long is the longest side (in cm)?
  2. 2.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  3. 3.In triangle ABC, angle A = 48° and angle B = 71°. What is angle C (in degrees)?
  4. 4.Can a triangle have sides of 9 cm, 11 cm and 3 cm? (a) Yes (b) No
  5. 5.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  10. 10.An exterior angle of a triangle is 140°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  11. 11.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  16. 16.In triangle ABC, angle A = 82° and angle B = 61°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 93° and angle B = 39°. What is angle C (in degrees)?
  20. 20.In triangle ABC, angle A = 48° and angle B = 98°. What is angle C (in degrees)?
  21. 21.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  22. 22.Can a triangle have sides of 17 cm, 9 cm and 8 cm? (a) No (b) Yes
  23. 23.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 27° and 41°. What is the exterior angle (in degrees)?
  27. 27.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  28. 28.In triangle ABC, angle A = 25° and angle B = 116°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 25° and angle B = 52°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 11 cm, 21 cm and 10 cm? (a) No (b) Yes
  31. 31.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  32. 32.In triangle ABC, angle A = 48° and angle B = 73°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 98° and angle B = 21°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 42° and angle B = 110°. What is angle C (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 87° and angle B = 67°. What is angle C (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 61° and 49°. What is the exterior angle (in degrees)?
  39. 39.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  40. 40.In triangle ABC, angle A = 39° and angle B = 94°. What is angle C (in degrees)?

Answer key

  1. 39
  2. 24
  3. 61
  4. Yes
  5. 77
  6. 84
  7. 69
  8. 36
  9. 17
  10. 71
  11. 36
  12. 100
  13. 70
  14. 26
  15. 66
  16. 37
  17. 38
  18. 102
  19. 48
  20. 34
  21. 5
  22. No
  23. 90
  24. 77
  25. 120
  26. 68
  27. 34
  28. 39
  29. 103
  30. No
  31. 80
  32. 59
  33. 61
  34. 24
  35. 28
  36. 110
  37. 26
  38. 110
  39. 58
  40. 47

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