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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 582 · 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 = 66° and angle B = 80°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  3. 3.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  4. 4.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  6. 6.The two interior opposite angles of a triangle are 23° and 68°. What is the exterior angle (in degrees)?
  7. 7.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  9. 9.In triangle ABC, angle A = 28° and angle B = 44°. What is angle C (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  12. 12.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  13. 13.In triangle ABC, angle A = 51° and angle B = 53°. What is angle C (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  17. 17.Can a triangle have sides of 12 cm, 20 cm and 4 cm? (a) Yes (b) No
  18. 18.In triangle ABC, angle A = 36° and angle B = 113°. What is angle C (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 8 cm, 8 cm and 11 cm? (a) Yes (b) No
  21. 21.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  22. 22.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  23. 23.In triangle ABC, angle A = 33° and angle B = 21°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  25. 25.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  26. 26.Can a triangle have sides of 11 cm, 14 cm and 2 cm? (a) Yes (b) No
  27. 27.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 65° and 64°. What is the exterior angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  34. 34.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)?
  35. 35.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  36. 36.In triangle ABC, angle A = 31° and angle B = 25°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 71° and angle B = 32°. What is angle C (in degrees)?

Answer key

  1. 34
  2. 50
  3. 15
  4. 20
  5. 26
  6. 91
  7. 53
  8. 20
  9. 108
  10. 67
  11. 27
  12. 24
  13. 76
  14. 61
  15. 19
  16. 69
  17. No
  18. 31
  19. 14
  20. Yes
  21. 72
  22. 78
  23. 126
  24. 36
  25. 70
  26. No
  27. 90
  28. 36
  29. 129
  30. 65
  31. 36
  32. 38
  33. 40
  34. 36
  35. 20
  36. 124
  37. 68
  38. 65
  39. 57
  40. 77

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