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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 3 · 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 a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  4. 4.Can a triangle have sides of 12 cm, 10 cm and 25 cm? (a) Yes (b) No
  5. 5.In triangle ABC, angle A = 28° and angle B = 70°. What is angle C (in degrees)?
  6. 6.Can a triangle have sides of 20 cm, 8 cm and 11 cm? (a) Yes (b) No
  7. 7.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  8. 8.Can a triangle have sides of 7 cm, 17 cm and 6 cm? (a) Yes (b) No
  9. 9.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  10. 10.In triangle ABC, angle A = 31° and angle B = 37°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 67° and angle B = 34°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  15. 15.Can a triangle have sides of 25 cm, 10 cm and 10 cm? (a) No (b) Yes
  16. 16.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 26° and angle B = 34°. What is angle C (in degrees)?
  18. 18.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 71° and 77°. What is the exterior angle (in degrees)?
  21. 21.In triangle ABC, angle A = 41° and angle B = 45°. What is angle C (in degrees)?
  22. 22.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  23. 23.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  24. 24.In triangle ABC, angle A = 35° and angle B = 46°. What is angle C (in degrees)?
  25. 25.Can a triangle have sides of 6 cm, 8 cm and 19 cm? (a) No (b) Yes
  26. 26.The two interior opposite angles of a triangle are 77° and 39°. What is the exterior angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 56° and 72°. What is the exterior angle (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 67° and 43°. What is the exterior angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 49° and 37°. What is the exterior angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 57° and angle B = 79°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 96° and angle B = 52°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 82° and angle B = 60°. What is angle C (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 23° and 36°. What is the exterior angle (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 31° and 77°. What is the exterior angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 71° and 74°. What is the exterior angle (in degrees)?

Answer key

  1. 27
  2. 60
  3. 78
  4. No
  5. 82
  6. No
  7. 72
  8. No
  9. 25
  10. 112
  11. 79
  12. 50
  13. 74
  14. 100
  15. No
  16. 44
  17. 120
  18. 44
  19. 40
  20. 148
  21. 94
  22. 36
  23. 50
  24. 99
  25. No
  26. 116
  27. 128
  28. 110
  29. 86
  30. 80
  31. 44
  32. 32
  33. 38
  34. 25
  35. 59
  36. 59
  37. 126
  38. 21
  39. 108
  40. 145

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