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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 161 · 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 two equal angles are 35° each. What is the third angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 53°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  4. 4.Can a triangle have sides of 8 cm, 16 cm and 6 cm? (a) No (b) Yes
  5. 5.Can a triangle have sides of 7 cm, 3 cm and 7 cm? (a) No (b) Yes
  6. 6.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 28° and angle B = 106°. What is angle C (in degrees)?
  11. 11.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  15. 15.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  16. 16.Can a triangle have sides of 8 cm, 8 cm and 20 cm? (a) No (b) Yes
  17. 17.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 100° and angle B = 29°. What is angle C (in degrees)?
  19. 19.Can a triangle have sides of 11 cm, 16 cm and 3 cm? (a) Yes (b) No
  20. 20.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 53° and angle B = 45°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 6 cm, 6 cm and 5 cm? (a) Yes (b) No
  23. 23.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  24. 24.Can a triangle have sides of 6 cm, 8 cm and 10 cm? (a) No (b) Yes
  25. 25.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 12 cm, 17 cm and 4 cm? (a) Yes (b) No
  27. 27.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  28. 28.In triangle ABC, angle A = 24° and angle B = 130°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  32. 32.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  33. 33.In triangle ABC, angle A = 21° and angle B = 92°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 2 cm, 7 cm and 10 cm? (a) Yes (b) No
  35. 35.In triangle ABC, angle A = 76° and angle B = 31°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 73° and angle B = 35°. What is angle C (in degrees)?
  37. 37.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  38. 38.Can a triangle have sides of 3 cm, 11 cm and 16 cm? (a) Yes (b) No
  39. 39.Can a triangle have sides of 13 cm, 4 cm and 8 cm? (a) Yes (b) No
  40. 40.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?

Answer key

  1. 110
  2. 90
  3. 26
  4. No
  5. Yes
  6. 53
  7. 41
  8. 43
  9. 40
  10. 46
  11. 31
  12. 26
  13. 23
  14. 79
  15. 34
  16. No
  17. 42
  18. 51
  19. No
  20. 18
  21. 82
  22. Yes
  23. 30
  24. Yes
  25. 18
  26. No
  27. 80
  28. 26
  29. 46
  30. 56
  31. 38
  32. 39
  33. 67
  34. No
  35. 73
  36. 72
  37. 56
  38. No
  39. No
  40. 94

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