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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 304 · 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 a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 32° and angle B = 87°. What is angle C (in degrees)?
  3. 3.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  4. 4.Can a triangle have sides of 7 cm, 6 cm and 3 cm? (a) Yes (b) No
  5. 5.In triangle ABC, angle A = 74° and angle B = 69°. What is angle C (in degrees)?
  6. 6.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 82° and angle B = 47°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 98°. What is each of the other two angles (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  12. 12.Can a triangle have sides of 9 cm, 20 cm and 11 cm? (a) No (b) Yes
  13. 13.In triangle ABC, angle A = 47° and angle B = 39°. What is angle C (in degrees)?
  14. 14.Can a triangle have sides of 15 cm, 3 cm and 12 cm? (a) Yes (b) No
  15. 15.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  17. 17.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)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  19. 19.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 3 cm, 2 cm and 5 cm? (a) Yes (b) No
  23. 23.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  24. 24.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 28° and 39°. What is the exterior angle (in degrees)?
  26. 26.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)?
  27. 27.Can a triangle have sides of 9 cm, 2 cm and 9 cm? (a) Yes (b) No
  28. 28.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 8 cm, 10 cm and 6 cm? (a) No (b) Yes
  30. 30.Can a triangle have sides of 2 cm, 11 cm and 4 cm? (a) Yes (b) No
  31. 31.In triangle ABC, angle A = 36° and angle B = 114°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 71° and 62°. What is the exterior angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 79° and angle B = 28°. What is angle C (in degrees)?
  38. 38.Can a triangle have sides of 15 cm, 7 cm and 8 cm? (a) Yes (b) No
  39. 39.Can a triangle have sides of 22 cm, 6 cm and 11 cm? (a) Yes (b) No
  40. 40.An exterior angle of a triangle is 128°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?

Answer key

  1. 54
  2. 61
  3. 71
  4. Yes
  5. 37
  6. 84
  7. 36
  8. 51
  9. 24
  10. 41
  11. 36
  12. No
  13. 94
  14. No
  15. 30
  16. 73
  17. 20
  18. 11
  19. 50
  20. 31
  21. 71
  22. No
  23. 65
  24. 32
  25. 67
  26. 36
  27. Yes
  28. 75
  29. Yes
  30. No
  31. 30
  32. 20
  33. 75
  34. 133
  35. 42
  36. 68
  37. 73
  38. No
  39. No
  40. 65

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