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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 881 · 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 = 60° and angle B = 70°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 24° and angle B = 50°. What is angle C (in degrees)?
  3. 3.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  4. 4.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  7. 7.In triangle ABC, angle A = 62° and angle B = 49°. What is angle C (in degrees)?
  8. 8.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  9. 9.In triangle ABC, angle A = 63° and angle B = 47°. What is angle C (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  12. 12.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  13. 13.In triangle ABC, angle A = 45° and angle B = 22°. What is angle C (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 35° and angle B = 91°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  17. 17.Can a triangle have sides of 6 cm, 2 cm and 5 cm? (a) No (b) Yes
  18. 18.Can a triangle have sides of 10 cm, 10 cm and 25 cm? (a) No (b) Yes
  19. 19.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)?
  20. 20.Can a triangle have sides of 12 cm, 12 cm and 6 cm? (a) Yes (b) No
  21. 21.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  22. 22.Can a triangle have sides of 9 cm, 21 cm and 12 cm? (a) Yes (b) No
  23. 23.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  24. 24.Can a triangle have sides of 8 cm, 22 cm and 9 cm? (a) Yes (b) No
  25. 25.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 54° and 49°. What is the exterior angle (in degrees)?
  28. 28.Can a triangle have sides of 16 cm, 8 cm and 8 cm? (a) Yes (b) No
  29. 29.An exterior angle of a triangle is 126°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  30. 30.Can a triangle have sides of 12 cm, 14 cm and 8 cm? (a) Yes (b) No
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  32. 32.In triangle ABC, angle A = 39° and angle B = 90°. What is angle C (in degrees)?
  33. 33.Can a triangle have sides of 5 cm, 12 cm and 9 cm? (a) Yes (b) No
  34. 34.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  36. 36.In triangle ABC, angle A = 82° and angle B = 70°. What is angle C (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 9 cm, 6 cm and 3 cm? (a) No (b) Yes
  39. 39.In triangle ABC, angle A = 95° and angle B = 40°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 9 cm, 5 cm and 5 cm? (a) Yes (b) No

Answer key

  1. 50
  2. 106
  3. 8
  4. 92
  5. 20
  6. 50
  7. 69
  8. 47
  9. 70
  10. 16
  11. 78
  12. 24
  13. 113
  14. 27
  15. 54
  16. 19
  17. Yes
  18. No
  19. 24
  20. Yes
  21. 5
  22. No
  23. 12
  24. No
  25. 66
  26. 14
  27. 103
  28. No
  29. 71
  30. Yes
  31. 40
  32. 51
  33. Yes
  34. 51
  35. 100
  36. 28
  37. 60
  38. No
  39. 45
  40. Yes

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