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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 376 · 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.

NameDateTime takenScore ___ / 40
  1. 1.Can a triangle have sides of 13 cm, 4 cm and 9 cm? (a) No (b) Yes
  2. 2.Can a triangle have sides of 5 cm, 9 cm and 10 cm? (a) No (b) Yes
  3. 3.Can a triangle have sides of 13 cm, 8 cm and 9 cm? (a) Yes (b) No
  4. 4.An exterior angle of a triangle is 142°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  5. 5.An exterior angle of a triangle is 144°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 20° and angle B = 100°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  9. 9.In triangle ABC, angle A = 87° and angle B = 38°. What is angle C (in degrees)?
  10. 10.Can a triangle have sides of 12 cm, 6 cm and 3 cm? (a) No (b) Yes
  11. 11.In triangle ABC, angle A = 25° and angle B = 33°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 10 cm, 10 cm and 24 cm? (a) No (b) Yes
  13. 13.Can a triangle have sides of 2 cm, 2 cm and 8 cm? (a) No (b) Yes
  14. 14.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  17. 17.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  19. 19.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  20. 20.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  22. 22.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  23. 23.In an isosceles triangle, the angle between the two equal sides is 46°. What is each of the other two angles (in degrees)?
  24. 24.In triangle ABC, angle A = 67° and angle B = 21°. What is angle C (in degrees)?
  25. 25.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  27. 27.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  28. 28.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 56° and 60°. What is the exterior angle (in degrees)?
  31. 31.In triangle ABC, angle A = 93° and angle B = 31°. What is angle C (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  34. 34.In triangle ABC, angle A = 69° and angle B = 70°. What is angle C (in degrees)?
  35. 35.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  37. 37.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)?
  38. 38.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  39. 39.In triangle ABC, angle A = 28° and angle B = 64°. What is angle C (in degrees)?
  40. 40.Can a triangle have sides of 3 cm, 9 cm and 10 cm? (a) Yes (b) No

Answer key

  1. No
  2. Yes
  3. Yes
  4. 80
  5. 76
  6. 10
  7. 60
  8. 90
  9. 55
  10. No
  11. 122
  12. No
  13. No
  14. 66
  15. 79
  16. 26
  17. 100
  18. 57
  19. 26
  20. 78
  21. 30
  22. 69
  23. 67
  24. 92
  25. 48
  26. 68
  27. 15
  28. 100
  29. 90
  30. 116
  31. 56
  32. 90
  33. 25
  34. 41
  35. 20
  36. 40
  37. 5
  38. 17
  39. 88
  40. Yes

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