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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 252 · 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 triangle ABC, angle A = 71° and angle B = 36°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 62° and 55°. What is the exterior angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 76° and angle B = 57°. What is angle C (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  7. 7.Can a triangle have sides of 23 cm, 10 cm and 11 cm? (a) Yes (b) No
  8. 8.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 24° and angle B = 60°. What is angle C (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  11. 11.In triangle ABC, angle A = 76° and angle B = 36°. What is angle C (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  13. 13.Can a triangle have sides of 4 cm, 3 cm and 7 cm? (a) Yes (b) No
  14. 14.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)?
  15. 15.Can a triangle have sides of 3 cm, 10 cm and 8 cm? (a) No (b) Yes
  16. 16.In triangle ABC, angle A = 29° and angle B = 32°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 73° and angle B = 62°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 58° and 34°. What is the exterior angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  22. 22.Can a triangle have sides of 14 cm, 10 cm and 6 cm? (a) Yes (b) No
  23. 23.In triangle ABC, angle A = 29° and angle B = 56°. What is angle C (in degrees)?
  24. 24.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  25. 25.Can a triangle have sides of 10 cm, 3 cm and 16 cm? (a) Yes (b) No
  26. 26.An exterior angle of a triangle is 54°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  28. 28.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 2 cm, 2 cm and 2 cm? (a) Yes (b) No
  30. 30.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  32. 32.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  34. 34.Can a triangle have sides of 8 cm, 3 cm and 4 cm? (a) Yes (b) No
  35. 35.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  36. 36.An exterior angle of a triangle is 133°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  38. 38.Can a triangle have sides of 11 cm, 6 cm and 21 cm? (a) Yes (b) No
  39. 39.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?

Answer key

  1. 73
  2. 100
  3. 117
  4. 63
  5. 47
  6. 120
  7. No
  8. 62
  9. 96
  10. 20
  11. 68
  12. 10
  13. No
  14. 36
  15. Yes
  16. 119
  17. 45
  18. 92
  19. 36
  20. 34
  21. 84
  22. Yes
  23. 95
  24. 24
  25. No
  26. 22
  27. 26
  28. 19
  29. Yes
  30. 40
  31. 17
  32. 36
  33. 55
  34. No
  35. 71
  36. 66
  37. 25
  38. No
  39. 90
  40. 58

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