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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 429 · 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.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  2. 2.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)?
  3. 3.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  4. 4.An exterior angle of a triangle is 58°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  5. 5.Can a triangle have sides of 15 cm, 3 cm and 7 cm? (a) No (b) Yes
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  7. 7.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)?
  8. 8.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  9. 9.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)?
  10. 10.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 12 cm, 6 cm and 9 cm? (a) No (b) Yes
  12. 12.In triangle ABC, angle A = 49° and angle B = 98°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  14. 14.In triangle ABC, angle A = 82° and angle B = 44°. What is angle C (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  17. 17.Can a triangle have sides of 9 cm, 5 cm and 4 cm? (a) Yes (b) No
  18. 18.In triangle ABC, angle A = 50° and angle B = 20°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 100° and angle B = 56°. What is angle C (in degrees)?
  20. 20.In triangle ABC, angle A = 45° and angle B = 96°. What is angle C (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  23. 23.Can a triangle have sides of 20 cm, 5 cm and 11 cm? (a) No (b) Yes
  24. 24.In triangle ABC, angle A = 43° and angle B = 110°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 58° and angle B = 84°. What is angle C (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 12 cm, 3 cm and 13 cm? (a) No (b) Yes
  28. 28.In triangle ABC, angle A = 22° and angle B = 49°. What is angle C (in degrees)?
  29. 29.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  30. 30.In triangle ABC, angle A = 51° and angle B = 66°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 93° and angle B = 23°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 37° and angle B = 119°. What is angle C (in degrees)?
  33. 33.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)?
  34. 34.In triangle ABC, angle A = 38° and angle B = 94°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  38. 38.In triangle ABC, angle A = 50° and angle B = 61°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 45° and 31°. What is the exterior angle (in degrees)?

Answer key

  1. 75
  2. 12
  3. 72
  4. 22
  5. No
  6. 20
  7. 15
  8. 90
  9. 8
  10. 132
  11. Yes
  12. 33
  13. 56
  14. 54
  15. 44
  16. 20
  17. No
  18. 110
  19. 24
  20. 39
  21. 25
  22. 76
  23. No
  24. 27
  25. 38
  26. 46
  27. Yes
  28. 109
  29. 45
  30. 63
  31. 64
  32. 24
  33. 24
  34. 48
  35. 20
  36. 46
  37. 90
  38. 69
  39. 120
  40. 76

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