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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 213 · 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 1 : 1 : 2. What is the biggest angle (in degrees)?
  2. 2.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  4. 4.Can a triangle have sides of 3 cm, 14 cm and 6 cm? (a) No (b) Yes
  5. 5.In triangle ABC, angle A = 87° and angle B = 35°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 144°. What is each of the other two angles (in degrees)?
  7. 7.An exterior angle of a triangle is 56°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  8. 8.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  9. 9.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  10. 10.Can a triangle have sides of 10 cm, 10 cm and 8 cm? (a) No (b) Yes
  11. 11.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  16. 16.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  17. 17.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 40° and 33°. What is the exterior angle (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  20. 20.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 12 cm, 23 cm and 10 cm? (a) Yes (b) No
  22. 22.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  23. 23.In triangle ABC, angle A = 25° and angle B = 90°. What is angle C (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  25. 25.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  28. 28.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  29. 29.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 36° and angle B = 96°. What is angle C (in degrees)?
  32. 32.Can a triangle have sides of 3 cm, 1 cm and 3 cm? (a) Yes (b) No
  33. 33.In triangle ABC, angle A = 25° and angle B = 81°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 10 cm, 6 cm and 7 cm? (a) No (b) Yes
  35. 35.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  39. 39.In triangle ABC, angle A = 94° and angle B = 60°. What is angle C (in degrees)?
  40. 40.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)?

Answer key

  1. 90
  2. 29
  3. 26
  4. No
  5. 58
  6. 18
  7. 31
  8. 70
  9. 61
  10. Yes
  11. 30
  12. 19
  13. 25
  14. 27
  15. 90
  16. 37
  17. 72
  18. 73
  19. 17
  20. 55
  21. No
  22. 30
  23. 65
  24. 25
  25. 79
  26. 66
  27. 66
  28. 69
  29. 72
  30. 75
  31. 48
  32. Yes
  33. 74
  34. Yes
  35. 130
  36. 73
  37. 72
  38. 30
  39. 26
  40. 15

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