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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 215 · 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 = 60° and angle B = 99°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  5. 5.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 44° and angle B = 49°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 27° and angle B = 88°. What is angle C (in degrees)?
  8. 8.Can a triangle have sides of 3 cm, 9 cm and 2 cm? (a) Yes (b) No
  9. 9.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 73° and angle B = 52°. What is angle C (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 58° and 35°. What is the exterior angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 78° and 62°. What is the exterior angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  16. 16.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  17. 17.Can a triangle have sides of 7 cm, 15 cm and 10 cm? (a) Yes (b) No
  18. 18.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 44° and 34°. What is the exterior angle (in degrees)?
  21. 21.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  24. 24.Can a triangle have sides of 3 cm, 15 cm and 11 cm? (a) Yes (b) No
  25. 25.In triangle ABC, angle A = 83° and angle B = 58°. What is angle C (in degrees)?
  26. 26.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)?
  27. 27.In triangle ABC, angle A = 50° and angle B = 78°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 23 cm, 10 cm and 12 cm? (a) No (b) Yes
  29. 29.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 79° and 55°. What is the exterior angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  33. 33.The two interior opposite angles of a triangle are 69° and 64°. What is the exterior angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 51° and 35°. What is the exterior angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  37. 37.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  38. 38.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  39. 39.In triangle ABC, angle A = 59° and angle B = 65°. What is angle C (in degrees)?
  40. 40.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?

Answer key

  1. 21
  2. 82
  3. 22
  4. 25
  5. 75
  6. 87
  7. 65
  8. No
  9. 106
  10. 55
  11. 93
  12. 90
  13. 140
  14. 80
  15. 47
  16. 21
  17. Yes
  18. 62
  19. 71
  20. 78
  21. 44
  22. 20
  23. 10
  24. No
  25. 39
  26. 7
  27. 52
  28. No
  29. 69
  30. 134
  31. 52
  32. 17
  33. 133
  34. 40
  35. 86
  36. 36
  37. 24
  38. 72
  39. 56
  40. 50

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