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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 402 · 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 = 28° and angle B = 90°. What is angle C (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.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  4. 4.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  6. 6.In triangle ABC, angle A = 34° and angle B = 47°. What is angle C (in degrees)?
  7. 7.Can a triangle have sides of 10 cm, 23 cm and 9 cm? (a) Yes (b) No
  8. 8.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  9. 9.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  10. 10.In triangle ABC, angle A = 84° and angle B = 41°. What is angle C (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 70° and angle B = 44°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 52° and angle B = 63°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 27° and angle B = 55°. What is angle C (in degrees)?
  16. 16.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 50° and angle B = 58°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 67° and angle B = 53°. What is angle C (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  23. 23.Can a triangle have sides of 10 cm, 4 cm and 15 cm? (a) Yes (b) No
  24. 24.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  28. 28.In an isosceles triangle, the two equal angles are 36° each. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 37° and angle B = 23°. What is angle C (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 56° each. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 35° and angle B = 89°. What is angle C (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  34. 34.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  36. 36.Can a triangle have sides of 9 cm, 16 cm and 10 cm? (a) No (b) Yes
  37. 37.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  39. 39.In triangle ABC, angle A = 99° and angle B = 31°. What is angle C (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?

Answer key

  1. 62
  2. 7
  3. 90
  4. 40
  5. 25
  6. 99
  7. No
  8. 15
  9. 8
  10. 55
  11. 100
  12. 38
  13. 66
  14. 65
  15. 98
  16. 36
  17. 14
  18. 29
  19. 72
  20. 36
  21. 60
  22. 45
  23. No
  24. 100
  25. 38
  26. 75
  27. 17
  28. 108
  29. 120
  30. 68
  31. 56
  32. 90
  33. 72
  34. 74
  35. 40
  36. Yes
  37. 22
  38. 42
  39. 50
  40. 56

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