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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 703 · 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 angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  2. 2.Can a triangle have sides of 8 cm, 3 cm and 5 cm? (a) Yes (b) No
  3. 3.In triangle ABC, angle A = 50° and angle B = 57°. What is angle C (in degrees)?
  4. 4.An exterior angle of a triangle is 127°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 29° and angle B = 95°. What is angle C (in degrees)?
  7. 7.Can a triangle have sides of 10 cm, 8 cm and 23 cm? (a) Yes (b) No
  8. 8.In triangle ABC, angle A = 24° and angle B = 34°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 36° and 56°. What is the exterior angle (in degrees)?
  11. 11.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  13. 13.An exterior angle of a triangle is 137°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 20 cm, 10 cm and 11 cm? (a) No (b) Yes
  16. 16.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 30° and angle B = 52°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 81° and angle B = 30°. What is angle C (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  21. 21.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  23. 23.Can a triangle have sides of 4 cm, 2 cm and 6 cm? (a) No (b) Yes
  24. 24.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  25. 25.Can a triangle have sides of 5 cm, 15 cm and 9 cm? (a) Yes (b) No
  26. 26.In triangle ABC, angle A = 28° and angle B = 97°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 7 cm, 12 cm and 7 cm? (a) Yes (b) No
  28. 28.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  29. 29.In triangle ABC, angle A = 24° and angle B = 89°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 7 cm, 8 cm and 19 cm? (a) No (b) Yes
  31. 31.In triangle ABC, angle A = 25° and angle B = 53°. What is angle C (in degrees)?
  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 an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  34. 34.In triangle ABC, angle A = 52° and angle B = 42°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  36. 36.In triangle ABC, angle A = 92° and angle B = 66°. What is angle C (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 70° and 78°. What is the exterior angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 65° and 23°. What is the exterior angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 65° and 37°. What is the exterior angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?

Answer key

  1. 36
  2. No
  3. 73
  4. 70
  5. 20
  6. 56
  7. No
  8. 122
  9. 74
  10. 92
  11. 28
  12. 30
  13. 78
  14. 106
  15. Yes
  16. 124
  17. 98
  18. 69
  19. 50
  20. 36
  21. 37
  22. 18
  23. No
  24. 36
  25. No
  26. 55
  27. Yes
  28. 20
  29. 67
  30. No
  31. 102
  32. 24
  33. 138
  34. 86
  35. 84
  36. 22
  37. 148
  38. 88
  39. 102
  40. 72

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