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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 707 · 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 triangle ABC, angle A = 73° and angle B = 76°. What is angle C (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  3. 3.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)?
  4. 4.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 81° and angle B = 41°. What is angle C (in degrees)?
  6. 6.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  9. 9.The longest side of a right-angled triangle is 25 cm and one of the other sides is 7 cm. How long is the third side (in cm)?
  10. 10.Can a triangle have sides of 11 cm, 9 cm and 24 cm? (a) No (b) Yes
  11. 11.In triangle ABC, angle A = 54° and angle B = 89°. What is angle C (in degrees)?
  12. 12.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  13. 13.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 21° and 67°. What is the exterior angle (in degrees)?
  15. 15.Can a triangle have sides of 4 cm, 3 cm and 9 cm? (a) No (b) Yes
  16. 16.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  21. 21.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  22. 22.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  25. 25.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  29. 29.In triangle ABC, angle A = 49° and angle B = 87°. What is angle C (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  31. 31.In triangle ABC, angle A = 50° and angle B = 72°. What is angle C (in degrees)?
  32. 32.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)?
  33. 33.The two interior opposite angles of a triangle are 27° and 61°. What is the exterior angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 31° and 41°. What is the exterior angle (in degrees)?
  35. 35.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  36. 36.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  37. 37.In triangle ABC, angle A = 97° and angle B = 52°. What is angle C (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  39. 39.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  40. 40.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?

Answer key

  1. 31
  2. 5
  3. 24
  4. 124
  5. 58
  6. 40
  7. 25
  8. 60
  9. 24
  10. No
  11. 37
  12. 10
  13. 90
  14. 88
  15. No
  16. 90
  17. 60
  18. 66
  19. 90
  20. 44
  21. 8
  22. 22
  23. 46
  24. 39
  25. 54
  26. 71
  27. 28
  28. 100
  29. 44
  30. 50
  31. 58
  32. 4
  33. 88
  34. 72
  35. 67
  36. 50
  37. 31
  38. 27
  39. 15
  40. 80

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