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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 726 · 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 an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  4. 4.In triangle ABC, angle A = 75° and angle B = 60°. What is angle C (in degrees)?
  5. 5.In a right-angled triangle, one of the other two angles is 56°. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  9. 9.Can a triangle have sides of 3 cm, 9 cm and 11 cm? (a) No (b) Yes
  10. 10.Can a triangle have sides of 8 cm, 8 cm and 20 cm? (a) No (b) Yes
  11. 11.Can a triangle have sides of 22 cm, 10 cm and 10 cm? (a) No (b) Yes
  12. 12.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)?
  13. 13.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  14. 14.In triangle ABC, angle A = 34° and angle B = 22°. What is angle C (in degrees)?
  15. 15.Can a triangle have sides of 6 cm, 16 cm and 7 cm? (a) No (b) Yes
  16. 16.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  17. 17.In triangle ABC, angle A = 42° and angle B = 101°. What is angle C (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  19. 19.Can a triangle have sides of 11 cm, 10 cm and 11 cm? (a) No (b) Yes
  20. 20.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  21. 21.In triangle ABC, angle A = 67° and angle B = 29°. What is angle C (in degrees)?
  22. 22.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 36° and angle B = 61°. What is angle C (in degrees)?
  25. 25.Can a triangle have sides of 7 cm, 10 cm and 15 cm? (a) No (b) Yes
  26. 26.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  27. 27.Can a triangle have sides of 4 cm, 9 cm and 11 cm? (a) No (b) Yes
  28. 28.In triangle ABC, angle A = 48° and angle B = 42°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 71° and angle B = 27°. What is angle C (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  31. 31.The two interior opposite angles of a triangle are 53° and 75°. What is the exterior angle (in degrees)?
  32. 32.In triangle ABC, angle A = 38° and angle B = 82°. What is angle C (in degrees)?
  33. 33.Can a triangle have sides of 21 cm, 11 cm and 10 cm? (a) No (b) Yes
  34. 34.In triangle ABC, angle A = 45° and angle B = 90°. What is angle C (in degrees)?
  35. 35.In triangle ABC, angle A = 88° and angle B = 45°. What is angle C (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  39. 39.In triangle ABC, angle A = 45° and angle B = 68°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?

Answer key

  1. 106
  2. 57
  3. 44
  4. 45
  5. 34
  6. 45
  7. 36
  8. 71
  9. Yes
  10. No
  11. No
  12. 8
  13. 36
  14. 124
  15. No
  16. 30
  17. 37
  18. 25
  19. Yes
  20. 45
  21. 84
  22. 72
  23. 124
  24. 83
  25. Yes
  26. 100
  27. Yes
  28. 90
  29. 82
  30. 17
  31. 128
  32. 60
  33. No
  34. 45
  35. 47
  36. 80
  37. 60
  38. 5
  39. 67
  40. 68

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