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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 232 · 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.In triangle ABC, angle A = 77° and angle B = 20°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 4 cm, 8 cm and 11 cm? (a) No (b) Yes
  3. 3.Can a triangle have sides of 9 cm, 10 cm and 3 cm? (a) No (b) Yes
  4. 4.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  6. 6.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)?
  7. 7.In triangle ABC, angle A = 70° and angle B = 48°. What is angle C (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 73° and 35°. What is the exterior angle (in degrees)?
  9. 9.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)?
  10. 10.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  12. 12.Can a triangle have sides of 11 cm, 5 cm and 10 cm? (a) Yes (b) No
  13. 13.In triangle ABC, angle A = 21° and angle B = 87°. What is angle C (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  16. 16.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)?
  17. 17.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  18. 18.Can a triangle have sides of 6 cm, 6 cm and 13 cm? (a) Yes (b) No
  19. 19.An exterior angle of a triangle is 63°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 54° and 72°. What is the exterior angle (in degrees)?
  21. 21.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  22. 22.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  25. 25.In triangle ABC, angle A = 98° and angle B = 27°. What is angle C (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  27. 27.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  28. 28.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  29. 29.In triangle ABC, angle A = 58° and angle B = 43°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 57° and angle B = 30°. What is angle C (in degrees)?
  31. 31.An exterior angle of a triangle is 52°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  32. 32.In triangle ABC, angle A = 28° and angle B = 21°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 42° and angle B = 23°. What is angle C (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  35. 35.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)?
  36. 36.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  37. 37.The two interior opposite angles of a triangle are 77° and 41°. What is the exterior angle (in degrees)?
  38. 38.In triangle ABC, angle A = 75° and angle B = 83°. What is angle C (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  40. 40.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?

Answer key

  1. 83
  2. Yes
  3. Yes
  4. 67
  5. 40
  6. 5
  7. 62
  8. 108
  9. 24
  10. 57
  11. 72
  12. Yes
  13. 72
  14. 41
  15. 65
  16. 15
  17. 13
  18. No
  19. 34
  20. 126
  21. 31
  22. 75
  23. 90
  24. 20
  25. 55
  26. 13
  27. 31
  28. 74
  29. 79
  30. 93
  31. 26
  32. 131
  33. 115
  34. 69
  35. 12
  36. 20
  37. 118
  38. 22
  39. 39
  40. 17

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