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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 479 · 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 4 cm, 3 cm and 5 cm? (a) Yes (b) No
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  4. 4.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  5. 5.The two interior opposite angles of a triangle are 29° and 79°. What is the exterior angle (in degrees)?
  6. 6.In triangle ABC, angle A = 86° and angle B = 31°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 82° and angle B = 20°. What is angle C (in degrees)?
  8. 8.Can a triangle have sides of 9 cm, 6 cm and 6 cm? (a) No (b) Yes
  9. 9.The two interior opposite angles of a triangle are 49° and 39°. What is the exterior angle (in degrees)?
  10. 10.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  11. 11.Can a triangle have sides of 12 cm, 16 cm and 9 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 79° and angle B = 79°. What is angle C (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  15. 15.In triangle ABC, angle A = 95° and angle B = 59°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 60° and angle B = 31°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 60° and angle B = 83°. What is angle C (in degrees)?
  18. 18.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  22. 22.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  23. 23.Can a triangle have sides of 13 cm, 2 cm and 11 cm? (a) Yes (b) No
  24. 24.The two interior opposite angles of a triangle are 31° and 53°. What is the exterior angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 70° and angle B = 59°. What is angle C (in degrees)?
  27. 27.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  28. 28.The two interior opposite angles of a triangle are 79° and 25°. What is the exterior angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 39° and angle B = 64°. What is angle C (in degrees)?
  31. 31.In triangle ABC, angle A = 82° and angle B = 50°. What is angle C (in degrees)?
  32. 32.Can a triangle have sides of 10 cm, 15 cm and 12 cm? (a) Yes (b) No
  33. 33.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  34. 34.Can a triangle have sides of 6 cm, 4 cm and 15 cm? (a) Yes (b) No
  35. 35.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  36. 36.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  38. 38.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 140°. What is each of the other two angles (in degrees)?
  40. 40.Can a triangle have sides of 7 cm, 9 cm and 3 cm? (a) No (b) Yes

Answer key

  1. Yes
  2. 80
  3. 49
  4. 8
  5. 108
  6. 63
  7. 78
  8. Yes
  9. 88
  10. 61
  11. Yes
  12. 22
  13. 48
  14. 80
  15. 26
  16. 89
  17. 37
  18. 68
  19. 120
  20. 90
  21. 25
  22. 90
  23. No
  24. 84
  25. 33
  26. 51
  27. 12
  28. 104
  29. 51
  30. 77
  31. 48
  32. Yes
  33. 90
  34. No
  35. 29
  36. 100
  37. 40
  38. 5
  39. 20
  40. Yes

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