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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 888 · 40 sums
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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 = 62° and angle B = 72°. What is angle C (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.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  5. 5.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 44° and angle B = 61°. What is angle C (in degrees)?
  7. 7.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)?
  8. 8.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  10. 10.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  13. 13.In triangle ABC, angle A = 75° and angle B = 23°. What is angle C (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  16. 16.Can a triangle have sides of 13 cm, 2 cm and 12 cm? (a) Yes (b) No
  17. 17.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 68° and 23°. What is the exterior angle (in degrees)?
  20. 20.In triangle ABC, angle A = 41° and angle B = 97°. What is angle C (in degrees)?
  21. 21.Can a triangle have sides of 16 cm, 7 cm and 5 cm? (a) Yes (b) No
  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.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  24. 24.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 12 cm, 5 cm and 17 cm? (a) Yes (b) No
  26. 26.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  27. 27.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  29. 29.In triangle ABC, angle A = 80° and angle B = 50°. What is angle C (in degrees)?
  30. 30.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  31. 31.Can a triangle have sides of 6 cm, 16 cm and 8 cm? (a) Yes (b) No
  32. 32.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  33. 33.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  34. 34.In triangle ABC, angle A = 25° and angle B = 46°. What is angle C (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 54° and 35°. What is the exterior angle (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  37. 37.Can a triangle have sides of 9 cm, 12 cm and 25 cm? (a) Yes (b) No
  38. 38.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?

Answer key

  1. 46
  2. 12
  3. 57
  4. 17
  5. 72
  6. 75
  7. 36
  8. 84
  9. 78
  10. 52
  11. 17
  12. 22
  13. 82
  14. 90
  15. 40
  16. Yes
  17. 63
  18. 52
  19. 91
  20. 42
  21. No
  22. 76
  23. 25
  24. 74
  25. No
  26. 71
  27. 9
  28. 16
  29. 50
  30. 33
  31. No
  32. 24
  33. 70
  34. 109
  35. 89
  36. 13
  37. No
  38. 25
  39. 40
  40. 100

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