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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 133 · 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 a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 86° and angle B = 56°. What is angle C (in degrees)?
  3. 3.Can a triangle have sides of 3 cm, 3 cm and 5 cm? (a) Yes (b) No
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 35° and angle B = 33°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 28° and angle B = 106°. What is angle C (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  10. 10.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  12. 12.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 27° and 59°. What is the exterior angle (in degrees)?
  14. 14.Can a triangle have sides of 8 cm, 6 cm and 14 cm? (a) No (b) Yes
  15. 15.Can a triangle have sides of 10 cm, 18 cm and 9 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 97° and angle B = 28°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 82° and angle B = 38°. What is angle C (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  21. 21.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  23. 23.Can a triangle have sides of 19 cm, 12 cm and 7 cm? (a) No (b) Yes
  24. 24.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  28. 28.In triangle ABC, angle A = 54° and angle B = 71°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  36. 36.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  37. 37.In triangle ABC, angle A = 82° and angle B = 67°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  39. 39.In triangle ABC, angle A = 44° and angle B = 75°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 5 cm, 8 cm and 3 cm? (a) No (b) Yes

Answer key

  1. 38
  2. 38
  3. Yes
  4. 80
  5. 112
  6. 92
  7. 46
  8. 27
  9. 15
  10. 64
  11. 20
  12. 27
  13. 86
  14. No
  15. Yes
  16. 55
  17. 60
  18. 56
  19. 31
  20. 90
  21. 55
  22. 23
  23. No
  24. 19
  25. 22
  26. 67
  27. 48
  28. 55
  29. 50
  30. 40
  31. 66
  32. 46
  33. 90
  34. 70
  35. 100
  36. 10
  37. 31
  38. 120
  39. 61
  40. No

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