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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 544 · 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 1 : 1 : 2. What is the smallest angle (in degrees)?
  2. 2.In triangle ABC, angle A = 83° and angle B = 61°. What is angle C (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 26° and angle B = 45°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 21° and angle B = 33°. What is angle C (in degrees)?
  6. 6.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  7. 7.Can a triangle have sides of 3 cm, 6 cm and 5 cm? (a) No (b) Yes
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  9. 9.In triangle ABC, angle A = 90° and angle B = 63°. What is angle C (in degrees)?
  10. 10.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)?
  11. 11.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  12. 12.Can a triangle have sides of 10 cm, 8 cm and 6 cm? (a) Yes (b) No
  13. 13.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  17. 17.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  19. 19.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)?
  20. 20.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  21. 21.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  24. 24.In triangle ABC, angle A = 72° and angle B = 47°. What is angle C (in degrees)?
  25. 25.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)?
  26. 26.Can a triangle have sides of 10 cm, 16 cm and 9 cm? (a) No (b) Yes
  27. 27.In triangle ABC, angle A = 53° and angle B = 48°. What is angle C (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 3 cm, 8 cm and 3 cm? (a) No (b) Yes
  30. 30.Can a triangle have sides of 6 cm, 15 cm and 4 cm? (a) No (b) Yes
  31. 31.In triangle ABC, angle A = 89° and angle B = 39°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  34. 34.Can a triangle have sides of 13 cm, 10 cm and 5 cm? (a) Yes (b) No
  35. 35.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 10 cm, 2 cm and 11 cm? (a) Yes (b) No
  37. 37.Can a triangle have sides of 8 cm, 4 cm and 5 cm? (a) Yes (b) No
  38. 38.In triangle ABC, angle A = 78° and angle B = 75°. What is angle C (in degrees)?
  39. 39.Can a triangle have sides of 5 cm, 4 cm and 8 cm? (a) Yes (b) No
  40. 40.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?

Answer key

  1. 45
  2. 36
  3. 22
  4. 109
  5. 126
  6. 50
  7. Yes
  8. 36
  9. 27
  10. 7
  11. 8
  12. Yes
  13. 71
  14. 21
  15. 90
  16. 80
  17. 20
  18. 30
  19. 24
  20. 25
  21. 70
  22. 140
  23. 13
  24. 61
  25. 10
  26. Yes
  27. 79
  28. 14
  29. No
  30. No
  31. 52
  32. 69
  33. 17
  34. Yes
  35. 74
  36. Yes
  37. Yes
  38. 27
  39. Yes
  40. 18

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