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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 155 · 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 26°. What is the third angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  4. 4.An exterior angle of a triangle is 81°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 47° and angle B = 58°. What is angle C (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  12. 12.In triangle ABC, angle A = 31° and angle B = 126°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 60° and angle B = 28°. What is angle C (in degrees)?
  14. 14.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)?
  15. 15.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 67° and angle B = 40°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 10 cm, 9 cm and 23 cm? (a) Yes (b) No
  20. 20.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  22. 22.Can a triangle have sides of 1 cm, 8 cm and 8 cm? (a) Yes (b) No
  23. 23.In triangle ABC, angle A = 41° and angle B = 118°. What is angle C (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 77° each. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 67° and angle B = 38°. What is angle C (in degrees)?
  27. 27.An exterior angle of a triangle is 68°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  28. 28.Can a triangle have sides of 2 cm, 4 cm and 5 cm? (a) No (b) Yes
  29. 29.In triangle ABC, angle A = 29° and angle B = 101°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 69° and angle B = 39°. What is angle C (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 12 cm, 4 cm and 9 cm? (a) No (b) Yes
  33. 33.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  34. 34.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  35. 35.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  36. 36.Can a triangle have sides of 4 cm, 1 cm and 4 cm? (a) No (b) Yes
  37. 37.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  38. 38.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?

Answer key

  1. 64
  2. 100
  3. 72
  4. 47
  5. 90
  6. 90
  7. 62
  8. 52
  9. 24
  10. 75
  11. 20
  12. 23
  13. 92
  14. 3
  15. 42
  16. 90
  17. 73
  18. 39
  19. No
  20. 48
  21. 15
  22. Yes
  23. 21
  24. 66
  25. 26
  26. 75
  27. 23
  28. Yes
  29. 50
  30. 72
  31. 80
  32. Yes
  33. 12
  34. 30
  35. 29
  36. Yes
  37. 25
  38. 32
  39. 37
  40. 84

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