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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 418 · 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.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  5. 5.In triangle ABC, angle A = 60° and angle B = 91°. What is angle C (in degrees)?
  6. 6.Can a triangle have sides of 7 cm, 3 cm and 10 cm? (a) No (b) Yes
  7. 7.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 72° and angle B = 40°. What is angle C (in degrees)?
  9. 9.Can a triangle have sides of 6 cm, 9 cm and 19 cm? (a) Yes (b) No
  10. 10.In triangle ABC, angle A = 31° and angle B = 73°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 53° and angle B = 24°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  14. 14.Can a triangle have sides of 8 cm, 6 cm and 13 cm? (a) Yes (b) No
  15. 15.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 11 cm, 7 cm and 6 cm? (a) No (b) Yes
  21. 21.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  22. 22.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  23. 23.Can a triangle have sides of 12 cm, 3 cm and 18 cm? (a) No (b) Yes
  24. 24.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 75° and 30°. What is the exterior angle (in degrees)?
  28. 28.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  29. 29.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  30. 30.In triangle ABC, angle A = 52° and angle B = 71°. What is angle C (in degrees)?
  31. 31.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  32. 32.Can a triangle have sides of 8 cm, 10 cm and 23 cm? (a) Yes (b) No
  33. 33.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  34. 34.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 24° and 24°. What is the exterior angle (in degrees)?
  36. 36.In triangle ABC, angle A = 83° and angle B = 25°. What is angle C (in degrees)?
  37. 37.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  38. 38.Can a triangle have sides of 10 cm, 24 cm and 10 cm? (a) No (b) Yes
  39. 39.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  40. 40.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?

Answer key

  1. 73
  2. 58
  3. 75
  4. 78
  5. 29
  6. No
  7. 30
  8. 68
  9. No
  10. 76
  11. 103
  12. 66
  13. 10
  14. Yes
  15. 102
  16. 18
  17. 68
  18. 48
  19. 46
  20. Yes
  21. 54
  22. 37
  23. No
  24. 110
  25. 30
  26. 20
  27. 105
  28. 35
  29. 5
  30. 57
  31. 49
  32. No
  33. 74
  34. 21
  35. 48
  36. 72
  37. 3
  38. No
  39. 28
  40. 60

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