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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 870 · 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 triangle ABC, angle A = 90° and angle B = 44°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 13 cm, 9 cm and 3 cm? (a) No (b) Yes
  3. 3.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 65° and 27°. What is the exterior angle (in degrees)?
  6. 6.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)?
  7. 7.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 10 cm, 7 cm and 14 cm? (a) No (b) Yes
  9. 9.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  10. 10.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  11. 11.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  12. 12.In triangle ABC, angle A = 89° and angle B = 61°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 47° and angle B = 33°. What is angle C (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 40° and 80°. What is the exterior angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  16. 16.Can a triangle have sides of 10 cm, 18 cm and 8 cm? (a) No (b) Yes
  17. 17.In triangle ABC, angle A = 47° and angle B = 25°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 10 cm, 12 cm and 9 cm? (a) Yes (b) No
  19. 19.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  21. 21.Can a triangle have sides of 15 cm, 4 cm and 6 cm? (a) Yes (b) No
  22. 22.In triangle ABC, angle A = 25° and angle B = 87°. What is angle C (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 60° and 37°. What is the exterior angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  26. 26.In triangle ABC, angle A = 20° and angle B = 73°. What is angle C (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  28. 28.Can a triangle have sides of 25 cm, 11 cm and 10 cm? (a) No (b) Yes
  29. 29.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  32. 32.Can a triangle have sides of 6 cm, 5 cm and 8 cm? (a) No (b) Yes
  33. 33.The two interior opposite angles of a triangle are 21° and 68°. What is the exterior angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 77° and 64°. What is the exterior angle (in degrees)?
  35. 35.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)?
  36. 36.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  37. 37.In triangle ABC, angle A = 97° and angle B = 37°. What is angle C (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  39. 39.Can a triangle have sides of 14 cm, 10 cm and 11 cm? (a) No (b) Yes
  40. 40.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?

Answer key

  1. 46
  2. No
  3. 100
  4. 59
  5. 92
  6. 15
  7. 58
  8. Yes
  9. 25
  10. 84
  11. 12
  12. 30
  13. 100
  14. 120
  15. 24
  16. No
  17. 108
  18. Yes
  19. 65
  20. 16
  21. No
  22. 68
  23. 97
  24. 39
  25. 120
  26. 87
  27. 10
  28. No
  29. 118
  30. 70
  31. 20
  32. Yes
  33. 89
  34. 141
  35. 24
  36. 36
  37. 46
  38. 10
  39. Yes
  40. 7

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