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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 216 · 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 = 77° and angle B = 62°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  3. 3.In triangle ABC, angle A = 64° and angle B = 76°. What is angle C (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 57°. What is the third 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 3 : 3 : 4. What is the biggest angle (in degrees)?
  7. 7.In triangle ABC, angle A = 72° and angle B = 25°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  9. 9.In triangle ABC, angle A = 59° and angle B = 80°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 66° and angle B = 31°. What is angle C (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 37° and angle B = 89°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 62° and angle B = 32°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 51° and angle B = 45°. What is angle C (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 67° and angle B = 77°. What is angle C (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  19. 19.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  21. 21.An exterior angle of a triangle is 129°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  24. 24.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  25. 25.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  29. 29.In triangle ABC, angle A = 66° and angle B = 39°. What is angle C (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 65° and 52°. What is the exterior angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  33. 33.In triangle ABC, angle A = 69° and angle B = 75°. What is angle C (in degrees)?
  34. 34.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 80° and 60°. What is the exterior angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 53° and 23°. What is the exterior angle (in degrees)?
  38. 38.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  39. 39.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  40. 40.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?

Answer key

  1. 41
  2. 20
  3. 40
  4. 33
  5. 90
  6. 72
  7. 83
  8. 50
  9. 41
  10. 83
  11. 84
  12. 46
  13. 54
  14. 86
  15. 84
  16. 45
  17. 36
  18. 25
  19. 22
  20. 57
  21. 66
  22. 10
  23. 13
  24. 65
  25. 64
  26. 45
  27. 31
  28. 20
  29. 75
  30. 117
  31. 24
  32. 71
  33. 36
  34. 8
  35. 20
  36. 140
  37. 76
  38. 12
  39. 25
  40. 19

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