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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 124 · 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.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  2. 2.The two interior opposite angles of a triangle are 58° and 77°. What is the exterior angle (in degrees)?
  3. 3.Can a triangle have sides of 11 cm, 7 cm and 6 cm? (a) No (b) Yes
  4. 4.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 24°. What is each of the other two angles (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  8. 8.Can a triangle have sides of 18 cm, 11 cm and 2 cm? (a) No (b) Yes
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  10. 10.An exterior angle of a triangle is 134°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  12. 12.Can a triangle have sides of 26 cm, 10 cm and 11 cm? (a) Yes (b) No
  13. 13.An exterior angle of a triangle is 41°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  14. 14.Can a triangle have sides of 10 cm, 6 cm and 21 cm? (a) No (b) Yes
  15. 15.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  16. 16.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)?
  17. 17.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  18. 18.Can a triangle have sides of 7 cm, 16 cm and 12 cm? (a) No (b) Yes
  19. 19.The two interior opposite angles of a triangle are 68° and 59°. What is the exterior angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 96° and angle B = 24°. What is angle C (in degrees)?
  22. 22.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  23. 23.Can a triangle have sides of 23 cm, 11 cm and 7 cm? (a) Yes (b) No
  24. 24.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 5 cm, 20 cm and 11 cm? (a) Yes (b) No
  27. 27.In triangle ABC, angle A = 28° and angle B = 79°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 91° and angle B = 27°. What is angle C (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 66° and angle B = 30°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 20° and angle B = 123°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  36. 36.In triangle ABC, angle A = 29° and angle B = 30°. What is angle C (in degrees)?
  37. 37.Can a triangle have sides of 2 cm, 9 cm and 6 cm? (a) Yes (b) No
  38. 38.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)?
  39. 39.The two shorter sides of a right-angled triangle are 12 cm and 9 cm. How long is the longest side (in cm)?
  40. 40.In triangle ABC, angle A = 70° and angle B = 87°. What is angle C (in degrees)?

Answer key

  1. 26
  2. 135
  3. Yes
  4. 8
  5. 78
  6. 73
  7. 28
  8. No
  9. 20
  10. 60
  11. 39
  12. No
  13. 20
  14. No
  15. 39
  16. 15
  17. 45
  18. Yes
  19. 127
  20. 59
  21. 60
  22. 48
  23. No
  24. 41
  25. 38
  26. No
  27. 73
  28. 62
  29. 20
  30. 60
  31. 84
  32. 37
  33. 100
  34. 13
  35. 24
  36. 121
  37. No
  38. 15
  39. 15
  40. 23

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