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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 153 · 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 48°. What is the third angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  3. 3.Can a triangle have sides of 3 cm, 3 cm and 3 cm? (a) No (b) Yes
  4. 4.In triangle ABC, angle A = 58° and angle B = 51°. What is angle C (in degrees)?
  5. 5.Can a triangle have sides of 12 cm, 15 cm and 7 cm? (a) No (b) Yes
  6. 6.In triangle ABC, angle A = 65° and angle B = 78°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  9. 9.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)?
  10. 10.In triangle ABC, angle A = 25° and angle B = 101°. What is angle C (in degrees)?
  11. 11.The two interior opposite angles of a triangle are 26° and 24°. What is the exterior angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  13. 13.An exterior angle of a triangle is 66°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  14. 14.Can a triangle have sides of 9 cm, 5 cm and 6 cm? (a) No (b) Yes
  15. 15.Can a triangle have sides of 12 cm, 2 cm and 10 cm? (a) Yes (b) No
  16. 16.In triangle ABC, angle A = 98° and angle B = 60°. What is angle C (in degrees)?
  17. 17.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  18. 18.Can a triangle have sides of 7 cm, 18 cm and 7 cm? (a) Yes (b) No
  19. 19.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  20. 20.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  21. 21.In triangle ABC, angle A = 50° and angle B = 94°. What is angle C (in degrees)?
  22. 22.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  23. 23.In triangle ABC, angle A = 24° and angle B = 37°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 71° and angle B = 59°. What is angle C (in degrees)?
  28. 28.Can a triangle have sides of 6 cm, 12 cm and 6 cm? (a) Yes (b) No
  29. 29.The two interior opposite angles of a triangle are 29° and 56°. What is the exterior angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 92° and angle B = 27°. What is angle C (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  33. 33.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  34. 34.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  35. 35.Can a triangle have sides of 7 cm, 14 cm and 2 cm? (a) No (b) Yes
  36. 36.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  38. 38.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  39. 39.An exterior angle of a triangle is 137°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  40. 40.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?

Answer key

  1. 42
  2. 36
  3. Yes
  4. 71
  5. Yes
  6. 37
  7. 44
  8. 18
  9. 24
  10. 54
  11. 50
  12. 48
  13. 41
  14. Yes
  15. No
  16. 22
  17. 5
  18. No
  19. 18
  20. 72
  21. 36
  22. 62
  23. 119
  24. 75
  25. 74
  26. 10
  27. 50
  28. No
  29. 85
  30. 72
  31. 61
  32. 57
  33. 12
  34. 36
  35. No
  36. 71
  37. 122
  38. 76
  39. 66
  40. 90

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