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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 777 · 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.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  4. 4.Can a triangle have sides of 3 cm, 5 cm and 4 cm? (a) No (b) Yes
  5. 5.The two interior opposite angles of a triangle are 80° and 73°. What is the exterior angle (in degrees)?
  6. 6.In triangle ABC, angle A = 51° and angle B = 45°. What is angle C (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 38° and 59°. What is the exterior angle (in degrees)?
  8. 8.Can a triangle have sides of 5 cm, 12 cm and 12 cm? (a) Yes (b) No
  9. 9.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  11. 11.An exterior angle of a triangle is 50°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  12. 12.In triangle ABC, angle A = 65° and angle B = 61°. What is angle C (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  14. 14.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  15. 15.In triangle ABC, angle A = 53° and angle B = 27°. What is angle C (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 34° and 75°. What is the exterior angle (in degrees)?
  17. 17.Can a triangle have sides of 19 cm, 9 cm and 11 cm? (a) No (b) Yes
  18. 18.In triangle ABC, angle A = 38° and angle B = 55°. What is angle C (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  20. 20.In triangle ABC, angle A = 71° and angle B = 56°. What is angle C (in degrees)?
  21. 21.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  23. 23.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 37° and 24°. What is the exterior angle (in degrees)?
  28. 28.In triangle ABC, angle A = 40° and angle B = 22°. What is angle C (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  30. 30.Can a triangle have sides of 6 cm, 3 cm and 11 cm? (a) No (b) Yes
  31. 31.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  32. 32.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  34. 34.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  35. 35.Can a triangle have sides of 15 cm, 6 cm and 8 cm? (a) Yes (b) No
  36. 36.In triangle ABC, angle A = 95° and angle B = 36°. What is angle C (in degrees)?
  37. 37.In triangle ABC, angle A = 94° and angle B = 23°. What is angle C (in degrees)?
  38. 38.In triangle ABC, angle A = 43° and angle B = 33°. What is angle C (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  40. 40.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?

Answer key

  1. 20
  2. 66
  3. 25
  4. Yes
  5. 153
  6. 84
  7. 97
  8. Yes
  9. 94
  10. 30
  11. 22
  12. 54
  13. 17
  14. 112
  15. 100
  16. 109
  17. Yes
  18. 87
  19. 27
  20. 53
  21. 15
  22. 50
  23. 58
  24. 42
  25. 49
  26. 75
  27. 61
  28. 118
  29. 40
  30. No
  31. 17
  32. 106
  33. 20
  34. 80
  35. No
  36. 49
  37. 63
  38. 104
  39. 62
  40. 36

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