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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 558 · 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 : 5 : 7. What is the biggest angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  3. 3.Can a triangle have sides of 5 cm, 2 cm and 5 cm? (a) Yes (b) No
  4. 4.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 73°. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 39° and angle B = 100°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  9. 9.Can a triangle have sides of 7 cm, 6 cm and 3 cm? (a) No (b) Yes
  10. 10.Can a triangle have sides of 6 cm, 8 cm and 6 cm? (a) Yes (b) No
  11. 11.Can a triangle have sides of 13 cm, 10 cm and 2 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 60° and angle B = 98°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  14. 14.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  15. 15.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 64° and angle B = 53°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  19. 19.Can a triangle have sides of 2 cm, 4 cm and 4 cm? (a) No (b) Yes
  20. 20.An exterior angle of a triangle is 83°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  21. 21.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  22. 22.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  23. 23.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  24. 24.In triangle ABC, angle A = 85° and angle B = 72°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  26. 26.In triangle ABC, angle A = 20° and angle B = 82°. What is angle C (in degrees)?
  27. 27.An exterior angle of a triangle is 135°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  28. 28.In triangle ABC, angle A = 44° and angle B = 24°. What is angle C (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 42° and 21°. What is the exterior angle (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  31. 31.Can a triangle have sides of 8 cm, 7 cm and 17 cm? (a) Yes (b) No
  32. 32.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  33. 33.In triangle ABC, angle A = 88° and angle B = 31°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 25° and angle B = 94°. What is angle C (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 79° and 63°. What is the exterior angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 29° and 70°. What is the exterior angle (in degrees)?
  37. 37.In triangle ABC, angle A = 30° and angle B = 38°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  40. 40.Can a triangle have sides of 7 cm, 4 cm and 13 cm? (a) Yes (b) No

Answer key

  1. 84
  2. 77
  3. Yes
  4. 46
  5. 17
  6. 41
  7. 61
  8. 15
  9. Yes
  10. Yes
  11. No
  12. 22
  13. 88
  14. 13
  15. 72
  16. 63
  17. 63
  18. 90
  19. Yes
  20. 47
  21. 4
  22. 66
  23. 32
  24. 23
  25. 30
  26. 78
  27. 79
  28. 112
  29. 63
  30. 5
  31. No
  32. 57
  33. 61
  34. 61
  35. 142
  36. 99
  37. 112
  38. 18
  39. 12
  40. No

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