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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 375 · 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 29°. What is the third angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 57° and 32°. What is the exterior angle (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  5. 5.In triangle ABC, angle A = 27° and angle B = 24°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  7. 7.Can a triangle have sides of 1 cm, 3 cm and 3 cm? (a) Yes (b) No
  8. 8.In triangle ABC, angle A = 97° and angle B = 45°. What is angle C (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 21° and 77°. What is the exterior angle (in degrees)?
  10. 10.In triangle ABC, angle A = 35° and angle B = 25°. What is angle C (in degrees)?
  11. 11.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  13. 13.Can a triangle have sides of 5 cm, 2 cm and 4 cm? (a) No (b) Yes
  14. 14.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 43° and 36°. What is the exterior angle (in degrees)?
  17. 17.In triangle ABC, angle A = 55° and angle B = 34°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 39° and 39°. What is the exterior angle (in degrees)?
  19. 19.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  20. 20.Can a triangle have sides of 5 cm, 9 cm and 9 cm? (a) Yes (b) No
  21. 21.An exterior angle of a triangle is 151°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  22. 22.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  23. 23.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 48° and 21°. What is the exterior angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 77° and 33°. What is the exterior angle (in degrees)?
  27. 27.In triangle ABC, angle A = 42° and angle B = 69°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 78° and angle B = 51°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 64° and angle B = 59°. What is angle C (in degrees)?
  30. 30.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  31. 31.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)?
  32. 32.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 26 cm, 10 cm and 12 cm? (a) Yes (b) No
  35. 35.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  36. 36.In triangle ABC, angle A = 35° and angle B = 120°. What is angle C (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 13 cm, 2 cm and 6 cm? (a) No (b) Yes
  39. 39.Can a triangle have sides of 2 cm, 7 cm and 3 cm? (a) No (b) Yes
  40. 40.An exterior angle of a triangle is 65°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?

Answer key

  1. 61
  2. 30
  3. 89
  4. 25
  5. 129
  6. 31
  7. Yes
  8. 38
  9. 98
  10. 120
  11. 33
  12. 80
  13. Yes
  14. 15
  15. 18
  16. 79
  17. 91
  18. 78
  19. 71
  20. Yes
  21. 71
  22. 39
  23. 61
  24. 53
  25. 69
  26. 110
  27. 69
  28. 51
  29. 57
  30. 48
  31. 3
  32. 80
  33. 64
  34. No
  35. 17
  36. 25
  37. 52
  38. No
  39. No
  40. 22

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