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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 965 · 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 56°. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 11 cm, 10 cm and 10 cm? (a) No (b) Yes
  3. 3.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 12 cm, 12 cm and 3 cm? (a) Yes (b) No
  5. 5.Can a triangle have sides of 19 cm, 8 cm and 6 cm? (a) No (b) Yes
  6. 6.In triangle ABC, angle A = 88° and angle B = 24°. What is angle C (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  8. 8.In triangle ABC, angle A = 33° and angle B = 56°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  11. 11.Can a triangle have sides of 10 cm, 5 cm and 8 cm? (a) No (b) Yes
  12. 12.In triangle ABC, angle A = 43° and angle B = 37°. What is angle C (in degrees)?
  13. 13.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  14. 14.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  15. 15.Can a triangle have sides of 5 cm, 3 cm and 8 cm? (a) Yes (b) No
  16. 16.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  17. 17.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  22. 22.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  23. 23.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 25° and angle B = 56°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 84° and angle B = 27°. What is angle C (in degrees)?
  26. 26.Can a triangle have sides of 6 cm, 7 cm and 14 cm? (a) No (b) Yes
  27. 27.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  28. 28.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  29. 29.In triangle ABC, angle A = 55° and angle B = 33°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 9 cm, 4 cm and 5 cm? (a) Yes (b) No
  31. 31.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  32. 32.Can a triangle have sides of 8 cm, 7 cm and 13 cm? (a) No (b) Yes
  33. 33.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  36. 36.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)?
  37. 37.In triangle ABC, angle A = 96° and angle B = 44°. What is angle C (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  40. 40.Can a triangle have sides of 5 cm, 7 cm and 4 cm? (a) No (b) Yes

Answer key

  1. 34
  2. Yes
  3. 16
  4. Yes
  5. No
  6. 68
  7. 5
  8. 91
  9. 41
  10. 22
  11. Yes
  12. 100
  13. 16
  14. 74
  15. No
  16. 31
  17. 45
  18. 39
  19. 84
  20. 19
  21. 76
  22. 20
  23. 82
  24. 99
  25. 69
  26. No
  27. 24
  28. 18
  29. 92
  30. No
  31. 25
  32. Yes
  33. 72
  34. 100
  35. 30
  36. 5
  37. 40
  38. 73
  39. 48
  40. Yes

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