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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 101 · 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 15 cm and 36 cm. How long is the longest side (in cm)?
  2. 2.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 42°. What is the other one (in degrees)?
  3. 3.Can a triangle have sides of 11 cm, 2 cm and 10 cm? (a) Yes (b) No
  4. 4.The two interior opposite angles of a triangle are 50° and 31°. What is the exterior angle (in degrees)?
  5. 5.Can a triangle have sides of 7 cm, 9 cm and 15 cm? (a) No (b) Yes
  6. 6.Can a triangle have sides of 17 cm, 11 cm and 10 cm? (a) Yes (b) No
  7. 7.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)?
  8. 8.In triangle ABC, angle A = 55° and angle B = 73°. What is angle C (in degrees)?
  9. 9.In triangle ABC, angle A = 44° and angle B = 87°. What is angle C (in degrees)?
  10. 10.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  14. 14.In triangle ABC, angle A = 46° and angle B = 60°. What is angle C (in degrees)?
  15. 15.An exterior angle of a triangle is 142°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  16. 16.An exterior angle of a triangle is 131°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  17. 17.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  18. 18.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  19. 19.In triangle ABC, angle A = 23° and angle B = 125°. What is angle C (in degrees)?
  20. 20.In triangle ABC, angle A = 57° and angle B = 44°. What is angle C (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 21° and 33°. What is the exterior angle (in degrees)?
  22. 22.The two interior opposite angles of a triangle are 35° and 78°. What is the exterior angle (in degrees)?
  23. 23.In triangle ABC, angle A = 58° and angle B = 36°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 7 cm, 19 cm and 10 cm? (a) Yes (b) No
  25. 25.The two interior opposite angles of a triangle are 78° and 76°. What is the exterior angle (in degrees)?
  26. 26.In triangle ABC, angle A = 64° and angle B = 30°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 32° and angle B = 32°. What is angle C (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 36° and 31°. What is the exterior angle (in degrees)?
  29. 29.In triangle ABC, angle A = 38° and angle B = 109°. What is angle C (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 54° and 47°. What is the exterior angle (in degrees)?
  32. 32.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  33. 33.Can a triangle have sides of 12 cm, 9 cm and 15 cm? (a) No (b) Yes
  34. 34.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  35. 35.In triangle ABC, angle A = 43° and angle B = 103°. What is angle C (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  37. 37.In triangle ABC, angle A = 23° and angle B = 62°. What is angle C (in degrees)?
  38. 38.In triangle ABC, angle A = 37° and angle B = 113°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 72° each. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?

Answer key

  1. 39
  2. 27
  3. Yes
  4. 81
  5. Yes
  6. Yes
  7. 24
  8. 52
  9. 49
  10. 80
  11. 49
  12. 58
  13. 72
  14. 74
  15. 71
  16. 67
  17. 54
  18. 47
  19. 32
  20. 79
  21. 54
  22. 113
  23. 86
  24. No
  25. 154
  26. 86
  27. 116
  28. 67
  29. 33
  30. 50
  31. 101
  32. 20
  33. Yes
  34. 75
  35. 34
  36. 70
  37. 95
  38. 30
  39. 36
  40. 84

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