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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 458 · 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 = 49° and angle B = 88°. What is angle C (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  3. 3.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 33° and 24°. What is the exterior angle (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 57° and 62°. What is the exterior angle (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 49° and 56°. What is the exterior angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 33° and 60°. What is the exterior angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 74° and angle B = 75°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 9 cm, 7 cm and 11 cm? (a) Yes (b) No
  13. 13.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  14. 14.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  15. 15.In triangle ABC, angle A = 28° and angle B = 72°. What is angle C (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  17. 17.In triangle ABC, angle A = 82° and angle B = 67°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  20. 20.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  21. 21.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)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  24. 24.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 66° and angle B = 90°. What is angle C (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  28. 28.Can a triangle have sides of 9 cm, 6 cm and 14 cm? (a) No (b) Yes
  29. 29.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 100° and angle B = 53°. What is angle C (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 32° and 45°. What is the exterior angle (in degrees)?
  32. 32.Can a triangle have sides of 7 cm, 19 cm and 9 cm? (a) Yes (b) No
  33. 33.The two shorter sides of a right-angled triangle are 20 cm and 15 cm. How long is the longest side (in cm)?
  34. 34.In an isosceles triangle, the two equal angles are 23° each. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?

Answer key

  1. 43
  2. 17
  3. 80
  4. 75
  5. 57
  6. 119
  7. 105
  8. 55
  9. 93
  10. 74
  11. 31
  12. Yes
  13. 12
  14. 35
  15. 80
  16. 79
  17. 31
  18. 90
  19. 59
  20. 15
  21. 24
  22. 40
  23. 20
  24. 15
  25. 20
  26. 24
  27. 20
  28. Yes
  29. 76
  30. 27
  31. 77
  32. No
  33. 25
  34. 134
  35. 78
  36. 100
  37. 54
  38. 67
  39. 26
  40. 44

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