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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 167 · 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 = 82° and angle B = 25°. 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 2 : 3 : 4. What is the smallest angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  5. 5.Can a triangle have sides of 18 cm, 9 cm and 9 cm? (a) Yes (b) No
  6. 6.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  7. 7.In triangle ABC, angle A = 93° and angle B = 64°. What is angle C (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  11. 11.An exterior angle of a triangle is 116°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  12. 12.In triangle ABC, angle A = 46° and angle B = 50°. What is angle C (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  14. 14.In triangle ABC, angle A = 39° and angle B = 45°. What is angle C (in degrees)?
  15. 15.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  16. 16.In triangle ABC, angle A = 96° and angle B = 62°. What is angle C (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 67° and 73°. What is the exterior angle (in degrees)?
  20. 20.In triangle ABC, angle A = 24° and angle B = 21°. What is angle C (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 50° each. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 5 cm, 5 cm and 13 cm? (a) No (b) Yes
  23. 23.In triangle ABC, angle A = 41° and angle B = 76°. What is angle C (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 55° and 62°. What is the exterior angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 61° and 41°. What is the exterior angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  29. 29.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  32. 32.Can a triangle have sides of 10 cm, 5 cm and 8 cm? (a) Yes (b) No
  33. 33.In triangle ABC, angle A = 83° and angle B = 74°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 10 cm, 20 cm and 8 cm? (a) Yes (b) No
  35. 35.The two interior opposite angles of a triangle are 45° and 43°. What is the exterior angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 40° and 62°. What is the exterior angle (in degrees)?
  37. 37.Can a triangle have sides of 9 cm, 1 cm and 9 cm? (a) No (b) Yes
  38. 38.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?

Answer key

  1. 73
  2. 7
  3. 40
  4. 36
  5. No
  6. 67
  7. 23
  8. 35
  9. 30
  10. 90
  11. 43
  12. 84
  13. 80
  14. 96
  15. 33
  16. 22
  17. 78
  18. 124
  19. 140
  20. 135
  21. 80
  22. No
  23. 63
  24. 117
  25. 64
  26. 102
  27. 76
  28. 77
  29. 22
  30. 61
  31. 56
  32. Yes
  33. 23
  34. No
  35. 88
  36. 102
  37. Yes
  38. 47
  39. 44
  40. 36

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