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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 961 · 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 43°. What is the third angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  4. 4.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 69° and angle B = 67°. What is angle C (in degrees)?
  7. 7.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)?
  8. 8.The two interior opposite angles of a triangle are 31° and 55°. What is the exterior angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  12. 12.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  13. 13.Can a triangle have sides of 11 cm, 14 cm and 3 cm? (a) Yes (b) No
  14. 14.Can a triangle have sides of 21 cm, 4 cm and 12 cm? (a) Yes (b) No
  15. 15.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  17. 17.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  18. 18.In triangle ABC, angle A = 42° and angle B = 102°. What is angle C (in degrees)?
  19. 19.An exterior angle of a triangle is 157°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  20. 20.In triangle ABC, angle A = 28° and angle B = 94°. What is angle C (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  22. 22.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 57° and angle B = 54°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 24° and angle B = 114°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 12 cm, 4 cm and 17 cm? (a) No (b) Yes
  28. 28.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  31. 31.In triangle ABC, angle A = 95° and angle B = 24°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 97° and angle B = 60°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 26° and angle B = 29°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 61° and angle B = 47°. What is angle C (in degrees)?
  37. 37.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  38. 38.Can a triangle have sides of 7 cm, 10 cm and 10 cm? (a) No (b) Yes
  39. 39.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?

Answer key

  1. 47
  2. 90
  3. 15
  4. 56
  5. 20
  6. 44
  7. 8
  8. 86
  9. 18
  10. 72
  11. 25
  12. 17
  13. No
  14. No
  15. 66
  16. 40
  17. 61
  18. 36
  19. 79
  20. 58
  21. 38
  22. 62
  23. 69
  24. 69
  25. 42
  26. 36
  27. No
  28. 58
  29. 80
  30. 24
  31. 61
  32. 23
  33. 70
  34. 60
  35. 125
  36. 72
  37. 47
  38. Yes
  39. 78
  40. 54

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