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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 102 · 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 4 : 5 : 6. What is the smallest angle (in degrees)?
  2. 2.Can a triangle have sides of 2 cm, 6 cm and 6 cm? (a) Yes (b) No
  3. 3.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 9 cm, 10 cm and 7 cm? (a) No (b) Yes
  5. 5.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  6. 6.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 60° and angle B = 94°. What is angle C (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 40° and 27°. What is the exterior angle (in degrees)?
  10. 10.Can a triangle have sides of 2 cm, 5 cm and 7 cm? (a) No (b) Yes
  11. 11.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  12. 12.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  13. 13.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 65° each. What is the third angle (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  17. 17.In triangle ABC, angle A = 33° and angle B = 42°. What is angle C (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  19. 19.Can a triangle have sides of 12 cm, 2 cm and 14 cm? (a) Yes (b) No
  20. 20.In triangle ABC, angle A = 52° and angle B = 33°. What is angle C (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 29° and 55°. What is the exterior angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  24. 24.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  25. 25.In triangle ABC, angle A = 90° and angle B = 42°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  27. 27.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  28. 28.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  29. 29.In triangle ABC, angle A = 64° and angle B = 47°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 62° and angle B = 93°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  33. 33.In triangle ABC, angle A = 24° and angle B = 94°. What is angle C (in degrees)?
  34. 34.In triangle ABC, angle A = 95° and angle B = 32°. What is angle C (in degrees)?
  35. 35.In triangle ABC, angle A = 88° and angle B = 28°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 85° and angle B = 24°. What is angle C (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 51° and 51°. What is the exterior angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 55° each. 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.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?

Answer key

  1. 48
  2. Yes
  3. 37
  4. Yes
  5. 16
  6. 75
  7. 54
  8. 26
  9. 67
  10. No
  11. 73
  12. 42
  13. 72
  14. 77
  15. 50
  16. 17
  17. 105
  18. 70
  19. No
  20. 95
  21. 84
  22. 46
  23. 27
  24. 47
  25. 48
  26. 22
  27. 8
  28. 100
  29. 69
  30. 25
  31. 36
  32. 13
  33. 62
  34. 53
  35. 64
  36. 71
  37. 102
  38. 70
  39. 63
  40. 90

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