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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 528 · 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 = 50° and angle B = 27°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  4. 4.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  5. 5.An exterior angle of a triangle is 58°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  7. 7.Can a triangle have sides of 19 cm, 12 cm and 8 cm? (a) No (b) Yes
  8. 8.In triangle ABC, angle A = 95° and angle B = 21°. What is angle C (in degrees)?
  9. 9.In triangle ABC, angle A = 34° and angle B = 53°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 47° and angle B = 38°. What is angle C (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 36° and 37°. What is the exterior angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  14. 14.In triangle ABC, angle A = 93° and angle B = 56°. What is angle C (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 64° and 40°. What is the exterior angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  17. 17.In triangle ABC, angle A = 20° and angle B = 55°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  19. 19.In triangle ABC, angle A = 93° and angle B = 28°. What is angle C (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 31° and angle B = 79°. What is angle C (in degrees)?
  23. 23.Can a triangle have sides of 6 cm, 13 cm and 4 cm? (a) Yes (b) No
  24. 24.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  25. 25.In triangle ABC, angle A = 37° and angle B = 96°. What is angle C (in degrees)?
  26. 26.Can a triangle have sides of 9 cm, 12 cm and 12 cm? (a) Yes (b) No
  27. 27.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  28. 28.In triangle ABC, angle A = 51° and angle B = 76°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 3 cm, 7 cm and 3 cm? (a) Yes (b) No
  32. 32.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  33. 33.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)?
  34. 34.In triangle ABC, angle A = 99° and angle B = 43°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  37. 37.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  40. 40.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?

Answer key

  1. 103
  2. 30
  3. 53
  4. 32
  5. 28
  6. 68
  7. Yes
  8. 64
  9. 93
  10. 95
  11. 73
  12. 40
  13. 15
  14. 31
  15. 104
  16. 37
  17. 105
  18. 84
  19. 59
  20. 70
  21. 58
  22. 70
  23. No
  24. 39
  25. 47
  26. Yes
  27. 71
  28. 53
  29. 61
  30. 16
  31. No
  32. 20
  33. 6
  34. 38
  35. 90
  36. 50
  37. 72
  38. 70
  39. 20
  40. 63

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