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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 598 · 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 63°. What is the third angle (in degrees)?
  2. 2.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)?
  3. 3.The two interior opposite angles of a triangle are 40° and 74°. What is the exterior angle (in degrees)?
  4. 4.In triangle ABC, angle A = 85° and angle B = 72°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  8. 8.In triangle ABC, angle A = 74° and angle B = 58°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  10. 10.In triangle ABC, angle A = 22° and angle B = 116°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 11 cm, 7 cm and 9 cm? (a) No (b) Yes
  12. 12.In triangle ABC, angle A = 68° and angle B = 90°. What is angle C (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  15. 15.Can a triangle have sides of 4 cm, 10 cm and 18 cm? (a) No (b) Yes
  16. 16.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  17. 17.Can a triangle have sides of 18 cm, 11 cm and 6 cm? (a) Yes (b) No
  18. 18.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 64°. What is each of the other two angles (in degrees)?
  20. 20.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  23. 23.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  24. 24.In triangle ABC, angle A = 52° and angle B = 33°. What is angle C (in degrees)?
  25. 25.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  26. 26.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  27. 27.Can a triangle have sides of 10 cm, 23 cm and 10 cm? (a) No (b) Yes
  28. 28.In triangle ABC, angle A = 100° and angle B = 50°. What is angle C (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 a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 47° and 52°. What is the exterior angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  34. 34.In triangle ABC, angle A = 61° and angle B = 25°. What is angle C (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 73° and 40°. What is the exterior angle (in degrees)?
  36. 36.Can a triangle have sides of 8 cm, 8 cm and 8 cm? (a) No (b) Yes
  37. 37.The two interior opposite angles of a triangle are 21° and 58°. What is the exterior angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 49° and angle B = 40°. What is angle C (in degrees)?

Answer key

  1. 27
  2. 7
  3. 114
  4. 23
  5. 12
  6. 52
  7. 100
  8. 48
  9. 11
  10. 42
  11. Yes
  12. 22
  13. 70
  14. 45
  15. No
  16. 75
  17. No
  18. 43
  19. 58
  20. 48
  21. 69
  22. 25
  23. 59
  24. 95
  25. 65
  26. 43
  27. No
  28. 30
  29. 80
  30. 66
  31. 106
  32. 99
  33. 30
  34. 94
  35. 113
  36. Yes
  37. 79
  38. 11
  39. 63
  40. 91

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