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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 619 · 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 3 : 3 : 4. What is the smallest angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 33° and 27°. What is the exterior angle (in degrees)?
  3. 3.In triangle ABC, angle A = 53° and angle B = 46°. What is angle C (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  5. 5.In triangle ABC, angle A = 57° and angle B = 64°. What is angle C (in degrees)?
  6. 6.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  7. 7.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  9. 9.Can a triangle have sides of 8 cm, 3 cm and 2 cm? (a) Yes (b) No
  10. 10.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  13. 13.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 74° each. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  17. 17.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  18. 18.An exterior angle of a triangle is 131°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  20. 20.Can a triangle have sides of 2 cm, 2 cm and 2 cm? (a) Yes (b) No
  21. 21.In triangle ABC, angle A = 92° and angle B = 54°. What is angle C (in degrees)?
  22. 22.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  23. 23.In triangle ABC, angle A = 70° and angle B = 81°. What is angle C (in degrees)?
  24. 24.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)?
  25. 25.Can a triangle have sides of 9 cm, 6 cm and 6 cm? (a) Yes (b) No
  26. 26.Can a triangle have sides of 8 cm, 1 cm and 8 cm? (a) Yes (b) No
  27. 27.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  29. 29.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  30. 30.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  31. 31.Can a triangle have sides of 5 cm, 10 cm and 12 cm? (a) No (b) Yes
  32. 32.In triangle ABC, angle A = 32° and angle B = 80°. What is angle C (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 33° each. What is the third angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  35. 35.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 27°. What is the other one (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 2 : 7 : 9. What is the smallest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 79° and angle B = 59°. What is angle C (in degrees)?
  39. 39.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?

Answer key

  1. 54
  2. 60
  3. 81
  4. 39
  5. 59
  6. 3
  7. 59
  8. 78
  9. No
  10. 20
  11. 32
  12. 62
  13. 21
  14. 52
  15. 32
  16. 45
  17. 27
  18. 58
  19. 120
  20. Yes
  21. 34
  22. 43
  23. 29
  24. 36
  25. Yes
  26. Yes
  27. 61
  28. 90
  29. 10
  30. 45
  31. Yes
  32. 68
  33. 114
  34. 45
  35. 28
  36. 90
  37. 20
  38. 42
  39. 70
  40. 68

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