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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 467 · 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 3 cm, 9 cm and 8 cm? (a) No (b) Yes
  2. 2.In triangle ABC, angle A = 48° and angle B = 45°. What is angle C (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 22° and 35°. What is the exterior angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  5. 5.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  6. 6.The two interior opposite angles of a triangle are 54° and 29°. What is the exterior angle (in degrees)?
  7. 7.In triangle ABC, angle A = 66° and angle B = 58°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 26° each. What is the third angle (in degrees)?
  11. 11.In triangle ABC, angle A = 86° and angle B = 36°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 7 cm, 19 cm and 12 cm? (a) No (b) Yes
  14. 14.Can a triangle have sides of 7 cm, 20 cm and 10 cm? (a) Yes (b) No
  15. 15.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 12 cm, 24 cm and 8 cm? (a) Yes (b) No
  21. 21.Can a triangle have sides of 2 cm, 6 cm and 3 cm? (a) No (b) Yes
  22. 22.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 64°. What is each of the other two angles (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  26. 26.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)?
  27. 27.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  29. 29.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  31. 31.In triangle ABC, angle A = 94° and angle B = 23°. What is angle C (in degrees)?
  32. 32.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  35. 35.Can a triangle have sides of 13 cm, 2 cm and 8 cm? (a) No (b) Yes
  36. 36.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  37. 37.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 32° and 50°. What is the exterior angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?

Answer key

  1. Yes
  2. 87
  3. 57
  4. 35
  5. 60
  6. 83
  7. 56
  8. 36
  9. 19
  10. 128
  11. 58
  12. 52
  13. No
  14. No
  15. 30
  16. 20
  17. 57
  18. 124
  19. 66
  20. No
  21. No
  22. 48
  23. 47
  24. 58
  25. 30
  26. 7
  27. 24
  28. 13
  29. 90
  30. 72
  31. 63
  32. 55
  33. 66
  34. 25
  35. No
  36. 14
  37. 50
  38. 36
  39. 82
  40. 54

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