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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 680 · 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 = 76° and angle B = 43°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  3. 3.Can a triangle have sides of 11 cm, 12 cm and 8 cm? (a) No (b) Yes
  4. 4.In triangle ABC, angle A = 76° and angle B = 40°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 81° and angle B = 24°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  7. 7.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)?
  8. 8.In triangle ABC, angle A = 89° and angle B = 66°. What is angle C (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 80° and 66°. What is the exterior angle (in degrees)?
  10. 10.In triangle ABC, angle A = 70° and angle B = 59°. What is angle C (in degrees)?
  11. 11.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  13. 13.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  15. 15.In triangle ABC, angle A = 87° and angle B = 53°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 46° and angle B = 108°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 8 cm, 2 cm and 14 cm? (a) Yes (b) No
  20. 20.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 72° and 24°. What is the exterior angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  23. 23.In triangle ABC, angle A = 57° and angle B = 37°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 76° and 27°. What is the exterior angle (in degrees)?
  26. 26.In triangle ABC, angle A = 97° and angle B = 54°. What is angle C (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  30. 30.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  31. 31.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 58°. What is the third angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  35. 35.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  36. 36.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)?
  37. 37.Can a triangle have sides of 10 cm, 12 cm and 22 cm? (a) No (b) Yes
  38. 38.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 36°. What is the other one (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.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?

Answer key

  1. 61
  2. 40
  3. Yes
  4. 64
  5. 75
  6. 29
  7. 5
  8. 25
  9. 146
  10. 51
  11. 13
  12. 63
  13. 36
  14. 60
  15. 40
  16. 26
  17. 44
  18. 28
  19. No
  20. 20
  21. 96
  22. 40
  23. 86
  24. 33
  25. 103
  26. 29
  27. 75
  28. 90
  29. 65
  30. 18
  31. 50
  32. 32
  33. 90
  34. 104
  35. 80
  36. 12
  37. No
  38. 72
  39. 37
  40. 73

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