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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 60 · 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 = 48° and angle B = 84°. What is angle C (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 65° and 50°. What is the exterior angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  4. 4.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 39° and 35°. What is the exterior angle (in degrees)?
  6. 6.Can a triangle have sides of 10 cm, 7 cm and 4 cm? (a) Yes (b) No
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 66°. 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 7 cm. How long is the third side (in cm)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  13. 13.In triangle ABC, angle A = 54° and angle B = 90°. What is angle C (in degrees)?
  14. 14.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  16. 16.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  18. 18.Can a triangle have sides of 9 cm, 6 cm and 6 cm? (a) Yes (b) No
  19. 19.Can a triangle have sides of 15 cm, 7 cm and 8 cm? (a) No (b) Yes
  20. 20.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 2 cm, 3 cm and 10 cm? (a) Yes (b) No
  22. 22.Can a triangle have sides of 12 cm, 18 cm and 2 cm? (a) Yes (b) No
  23. 23.The two interior opposite angles of a triangle are 72° and 54°. What is the exterior angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  25. 25.In triangle ABC, angle A = 62° and angle B = 69°. What is angle C (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  27. 27.In triangle ABC, angle A = 25° and angle B = 121°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 12 cm, 9 cm and 9 cm? (a) Yes (b) No
  29. 29.In triangle ABC, angle A = 34° and angle B = 24°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 10 cm, 9 cm and 8 cm? (a) Yes (b) No
  31. 31.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 50° and angle B = 70°. What is angle C (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 38° each. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  35. 35.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)?
  36. 36.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  37. 37.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)?
  38. 38.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 55° and angle B = 90°. What is angle C (in degrees)?

Answer key

  1. 48
  2. 115
  3. 72
  4. 42
  5. 74
  6. Yes
  7. 36
  8. 90
  9. 29
  10. 24
  11. 24
  12. 79
  13. 36
  14. 10
  15. 45
  16. 46
  17. 120
  18. Yes
  19. No
  20. 49
  21. No
  22. No
  23. 126
  24. 67
  25. 49
  26. 25
  27. 34
  28. Yes
  29. 122
  30. Yes
  31. 73
  32. 60
  33. 104
  34. 22
  35. 3
  36. 63
  37. 7
  38. 124
  39. 66
  40. 35

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