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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 811 · 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 74°. What is the third angle (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 79° and 51°. What is the exterior angle (in degrees)?
  3. 3.Can a triangle have sides of 11 cm, 10 cm and 9 cm? (a) No (b) Yes
  4. 4.Can a triangle have sides of 10 cm, 5 cm and 10 cm? (a) No (b) Yes
  5. 5.In triangle ABC, angle A = 93° and angle B = 39°. What is angle C (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 79° and 37°. What is the exterior angle (in degrees)?
  7. 7.In triangle ABC, angle A = 29° and angle B = 111°. What is angle C (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  9. 9.Can a triangle have sides of 9 cm, 24 cm and 10 cm? (a) Yes (b) No
  10. 10.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  11. 11.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  12. 12.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 8 cm, 3 cm and 6 cm? (a) Yes (b) No
  14. 14.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  19. 19.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)?
  20. 20.In triangle ABC, angle A = 46° and angle B = 60°. What is angle C (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 76° and angle B = 62°. What is angle C (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  25. 25.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  26. 26.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  27. 27.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 76° each. What is the third angle (in degrees)?
  29. 29.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)?
  30. 30.Can a triangle have sides of 20 cm, 8 cm and 10 cm? (a) Yes (b) No
  31. 31.Can a triangle have sides of 10 cm, 4 cm and 8 cm? (a) No (b) Yes
  32. 32.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  33. 33.Can a triangle have sides of 22 cm, 11 cm and 10 cm? (a) No (b) Yes
  34. 34.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 8 cm, 11 cm and 5 cm? (a) No (b) Yes
  37. 37.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  38. 38.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  39. 39.Can a triangle have sides of 21 cm, 5 cm and 12 cm? (a) No (b) Yes
  40. 40.In triangle ABC, angle A = 25° and angle B = 71°. What is angle C (in degrees)?

Answer key

  1. 16
  2. 130
  3. Yes
  4. Yes
  5. 48
  6. 116
  7. 40
  8. 76
  9. No
  10. 16
  11. 7
  12. 47
  13. Yes
  14. 28
  15. 124
  16. 79
  17. 90
  18. 11
  19. 8
  20. 74
  21. 18
  22. 42
  23. 86
  24. 50
  25. 3
  26. 30
  27. 66
  28. 28
  29. 24
  30. No
  31. Yes
  32. 20
  33. No
  34. 68
  35. 37
  36. Yes
  37. 78
  38. 36
  39. No
  40. 84

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