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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 287 · 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 92°. What is each of the other two angles (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  4. 4.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 92° and angle B = 21°. What is angle C (in degrees)?
  6. 6.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  7. 7.In triangle ABC, angle A = 72° and angle B = 36°. What is angle C (in degrees)?
  8. 8.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)?
  9. 9.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 12 cm, 5 cm and 12 cm? (a) Yes (b) No
  12. 12.Can a triangle have sides of 2 cm, 2 cm and 2 cm? (a) Yes (b) No
  13. 13.Can a triangle have sides of 2 cm, 4 cm and 5 cm? (a) Yes (b) No
  14. 14.In triangle ABC, angle A = 40° and angle B = 32°. What is angle C (in degrees)?
  15. 15.Can a triangle have sides of 9 cm, 6 cm and 19 cm? (a) Yes (b) No
  16. 16.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 57° and 70°. What is the exterior angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  21. 21.Can a triangle have sides of 11 cm, 10 cm and 23 cm? (a) No (b) Yes
  22. 22.The two interior opposite angles of a triangle are 40° and 69°. What is the exterior angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  24. 24.In triangle ABC, angle A = 57° and angle B = 75°. What is angle C (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  27. 27.Can a triangle have sides of 7 cm, 6 cm and 3 cm? (a) No (b) Yes
  28. 28.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  29. 29.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  30. 30.In triangle ABC, angle A = 75° and angle B = 34°. What is angle C (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 86° and angle B = 41°. What is angle C (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 25° and 43°. What is the exterior angle (in degrees)?
  37. 37.Can a triangle have sides of 8 cm, 11 cm and 4 cm? (a) No (b) Yes
  38. 38.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  40. 40.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?

Answer key

  1. 44
  2. 48
  3. 13
  4. 68
  5. 67
  6. 70
  7. 72
  8. 36
  9. 72
  10. 30
  11. Yes
  12. Yes
  13. Yes
  14. 108
  15. No
  16. 42
  17. 25
  18. 27
  19. 127
  20. 30
  21. No
  22. 109
  23. 75
  24. 48
  25. 80
  26. 90
  27. Yes
  28. 25
  29. 100
  30. 71
  31. 79
  32. 75
  33. 90
  34. 134
  35. 53
  36. 68
  37. Yes
  38. 11
  39. 72
  40. 54

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