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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 385 · 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 : 5 : 7. What is the smallest angle (in degrees)?
  2. 2.In triangle ABC, angle A = 84° and angle B = 60°. What is angle C (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  4. 4.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?
  5. 5.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)?
  6. 6.In triangle ABC, angle A = 100° and angle B = 45°. What is angle C (in degrees)?
  7. 7.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 95° and angle B = 62°. What is angle C (in degrees)?
  10. 10.Can a triangle have sides of 6 cm, 12 cm and 7 cm? (a) No (b) Yes
  11. 11.In triangle ABC, angle A = 94° and angle B = 45°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 24° and angle B = 66°. What is angle C (in degrees)?
  13. 13.Can a triangle have sides of 10 cm, 10 cm and 20 cm? (a) No (b) Yes
  14. 14.Can a triangle have sides of 4 cm, 12 cm and 21 cm? (a) No (b) Yes
  15. 15.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  16. 16.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 81° and angle B = 67°. What is angle C (in degrees)?
  19. 19.In triangle ABC, angle A = 93° and angle B = 60°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 5 cm, 7 cm and 10 cm? (a) No (b) Yes
  21. 21.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  23. 23.Can a triangle have sides of 10 cm, 9 cm and 10 cm? (a) Yes (b) No
  24. 24.In triangle ABC, angle A = 67° and angle B = 65°. What is angle C (in degrees)?
  25. 25.Can a triangle have sides of 4 cm, 18 cm and 9 cm? (a) Yes (b) No
  26. 26.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  28. 28.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  29. 29.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)?
  30. 30.In triangle ABC, angle A = 31° and angle B = 82°. What is angle C (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 49° and angle B = 43°. What is angle C (in degrees)?
  33. 33.In triangle ABC, angle A = 95° and angle B = 39°. What is angle C (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  36. 36.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)?
  37. 37.Can a triangle have sides of 11 cm, 10 cm and 4 cm? (a) Yes (b) No
  38. 38.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 52° each. What is the third angle (in degrees)?
  40. 40.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)?

Answer key

  1. 36
  2. 36
  3. 15
  4. 45
  5. 24
  6. 35
  7. 20
  8. 33
  9. 23
  10. Yes
  11. 41
  12. 90
  13. No
  14. No
  15. 53
  16. 78
  17. 50
  18. 32
  19. 27
  20. Yes
  21. 48
  22. 73
  23. Yes
  24. 48
  25. No
  26. 58
  27. 11
  28. 13
  29. 12
  30. 67
  31. 84
  32. 88
  33. 46
  34. 80
  35. 20
  36. 15
  37. Yes
  38. 18
  39. 76
  40. 20

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