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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 420 · 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 160°. What is each of the other two angles (in degrees)?
  2. 2.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  3. 3.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  4. 4.In triangle ABC, angle A = 73° and angle B = 70°. What is angle C (in degrees)?
  5. 5.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  6. 6.The two interior opposite angles of a triangle are 47° and 28°. What is the exterior angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  9. 9.Can a triangle have sides of 1 cm, 7 cm and 7 cm? (a) No (b) Yes
  10. 10.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 29° and angle B = 54°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 70° each. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 17 cm, 9 cm and 8 cm? (a) Yes (b) No
  14. 14.Can a triangle have sides of 23 cm, 8 cm and 12 cm? (a) No (b) Yes
  15. 15.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  16. 16.Can a triangle have sides of 5 cm, 3 cm and 6 cm? (a) Yes (b) No
  17. 17.In triangle ABC, angle A = 35° and angle B = 77°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 10 cm, 2 cm and 17 cm? (a) No (b) Yes
  19. 19.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  20. 20.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  22. 22.Can a triangle have sides of 10 cm, 2 cm and 3 cm? (a) No (b) Yes
  23. 23.In triangle ABC, angle A = 52° and angle B = 32°. What is angle C (in degrees)?
  24. 24.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  25. 25.Can a triangle have sides of 4 cm, 15 cm and 6 cm? (a) Yes (b) No
  26. 26.In triangle ABC, angle A = 84° and angle B = 34°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 5 cm, 7 cm and 3 cm? (a) Yes (b) No
  28. 28.The two interior opposite angles of a triangle are 45° and 23°. What is the exterior angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 64° and 48°. What is the exterior angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 53° and 33°. What is the exterior angle (in degrees)?
  33. 33.In triangle ABC, angle A = 53° and angle B = 69°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 71° and angle B = 52°. What is angle C (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 56° and angle B = 92°. What is angle C (in degrees)?
  39. 39.In triangle ABC, angle A = 77° and angle B = 50°. What is angle C (in degrees)?
  40. 40.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)?

Answer key

  1. 10
  2. 7
  3. 26
  4. 37
  5. 20
  6. 75
  7. 65
  8. 48
  9. Yes
  10. 56
  11. 97
  12. 40
  13. No
  14. No
  15. 100
  16. Yes
  17. 68
  18. No
  19. 84
  20. 72
  21. 45
  22. No
  23. 96
  24. 24
  25. No
  26. 62
  27. Yes
  28. 68
  29. 38
  30. 112
  31. 14
  32. 86
  33. 58
  34. 57
  35. 46
  36. 37
  37. 49
  38. 32
  39. 53
  40. 10

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