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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 110 · 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 angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  3. 3.Can a triangle have sides of 12 cm, 25 cm and 8 cm? (a) Yes (b) No
  4. 4.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)?
  5. 5.An exterior angle of a triangle is 82°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  6. 6.Can a triangle have sides of 12 cm, 6 cm and 23 cm? (a) Yes (b) No
  7. 7.In triangle ABC, angle A = 77° and angle B = 38°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 31° and 66°. What is the exterior angle (in degrees)?
  11. 11.In triangle ABC, angle A = 31° and angle B = 52°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  13. 13.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 79° and 51°. What is the exterior angle (in degrees)?
  15. 15.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)?
  16. 16.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  17. 17.In triangle ABC, angle A = 92° and angle B = 56°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 10 cm, 3 cm and 16 cm? (a) No (b) Yes
  20. 20.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 89° and angle B = 49°. What is angle C (in degrees)?
  24. 24.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 29°. What is the other one (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 = 39° and angle B = 59°. What is angle C (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 40° and 31°. What is the exterior angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 28° and angle B = 50°. What is angle C (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  32. 32.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  33. 33.Can a triangle have sides of 6 cm, 6 cm and 4 cm? (a) No (b) Yes
  34. 34.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  35. 35.Can a triangle have sides of 18 cm, 7 cm and 10 cm? (a) Yes (b) No
  36. 36.In triangle ABC, angle A = 55° and angle B = 100°. What is angle C (in degrees)?
  37. 37.Can a triangle have sides of 3 cm, 9 cm and 8 cm? (a) Yes (b) No
  38. 38.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  39. 39.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  40. 40.In triangle ABC, angle A = 57° and angle B = 99°. What is angle C (in degrees)?

Answer key

  1. 45
  2. 38
  3. No
  4. 7
  5. 53
  6. No
  7. 65
  8. 50
  9. 90
  10. 97
  11. 97
  12. 72
  13. 22
  14. 130
  15. 15
  16. 57
  17. 32
  18. 78
  19. No
  20. 80
  21. 100
  22. 66
  23. 42
  24. 46
  25. 120
  26. 82
  27. 79
  28. 71
  29. 39
  30. 102
  31. 18
  32. 45
  33. Yes
  34. 10
  35. No
  36. 25
  37. Yes
  38. 31
  39. 10
  40. 24

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