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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 546 · 40 sums
TalentJR

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 angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  2. 2.In triangle ABC, angle A = 22° and angle B = 83°. What is angle C (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 65° and 36°. What is the exterior angle (in degrees)?
  4. 4.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  5. 5.Can a triangle have sides of 14 cm, 6 cm and 4 cm? (a) No (b) Yes
  6. 6.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  7. 7.Can a triangle have sides of 8 cm, 12 cm and 9 cm? (a) Yes (b) No
  8. 8.The two interior opposite angles of a triangle are 39° and 35°. What is the exterior angle (in degrees)?
  9. 9.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  10. 10.Can a triangle have sides of 7 cm, 14 cm and 10 cm? (a) No (b) Yes
  11. 11.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  13. 13.Can a triangle have sides of 6 cm, 3 cm and 8 cm? (a) Yes (b) No
  14. 14.Can a triangle have sides of 6 cm, 5 cm and 3 cm? (a) Yes (b) No
  15. 15.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  17. 17.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  18. 18.Can a triangle have sides of 10 cm, 6 cm and 20 cm? (a) No (b) Yes
  19. 19.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  20. 20.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  21. 21.In triangle ABC, angle A = 61° and angle B = 29°. What is angle C (in degrees)?
  22. 22.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  23. 23.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  25. 25.Can a triangle have sides of 17 cm, 9 cm and 9 cm? (a) No (b) Yes
  26. 26.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  27. 27.An exterior angle of a triangle is 134°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 75° and angle B = 39°. What is angle C (in degrees)?
  31. 31.Can a triangle have sides of 3 cm, 8 cm and 13 cm? (a) Yes (b) No
  32. 32.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  33. 33.In triangle ABC, angle A = 65° and angle B = 22°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 6 cm, 7 cm and 15 cm? (a) Yes (b) No
  35. 35.In triangle ABC, angle A = 68° and angle B = 21°. What is angle C (in degrees)?
  36. 36.An exterior angle of a triangle is 132°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  37. 37.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 29°. What is the other one (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.In triangle ABC, angle A = 72° and angle B = 54°. What is angle C (in degrees)?
  40. 40.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?

Answer key

  1. 36
  2. 75
  3. 101
  4. 63
  5. No
  6. 70
  7. Yes
  8. 74
  9. 80
  10. Yes
  11. 122
  12. 84
  13. Yes
  14. Yes
  15. 45
  16. 39
  17. 17
  18. No
  19. 41
  20. 77
  21. 90
  22. 6
  23. 72
  24. 57
  25. Yes
  26. 40
  27. 55
  28. 10
  29. 116
  30. 66
  31. No
  32. 24
  33. 93
  34. No
  35. 91
  36. 52
  37. 75
  38. 30
  39. 54
  40. 13

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