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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 398 · 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.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  2. 2.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  3. 3.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 23° and 26°. What is the exterior angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  7. 7.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  8. 8.In an isosceles triangle, the two equal angles are 59° each. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  12. 12.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)?
  13. 13.In triangle ABC, angle A = 79° and angle B = 59°. What is angle C (in degrees)?
  14. 14.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  15. 15.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  16. 16.Can a triangle have sides of 11 cm, 2 cm and 5 cm? (a) Yes (b) No
  17. 17.In triangle ABC, angle A = 50° and angle B = 20°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  20. 20.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 75° and angle B = 44°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 58° and angle B = 37°. 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, 9 cm and 9 cm? (a) Yes (b) No
  26. 26.In triangle ABC, angle A = 45° and angle B = 53°. What is angle C (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  29. 29.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  31. 31.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  32. 32.In triangle ABC, angle A = 28° and angle B = 24°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 43° and angle B = 102°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 75° and angle B = 22°. What is angle C (in degrees)?
  39. 39.Can a triangle have sides of 3 cm, 10 cm and 12 cm? (a) No (b) Yes
  40. 40.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?

Answer key

  1. 50
  2. 24
  3. 36
  4. 49
  5. 90
  6. 20
  7. 24
  8. 62
  9. 46
  10. 17
  11. 20
  12. 7
  13. 42
  14. 6
  15. 36
  16. No
  17. 110
  18. 40
  19. 75
  20. 90
  21. 61
  22. 24
  23. 85
  24. 24
  25. Yes
  26. 82
  27. 66
  28. 62
  29. 52
  30. 69
  31. 36
  32. 128
  33. 35
  34. 52
  35. 57
  36. 90
  37. 18
  38. 83
  39. Yes
  40. 25

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