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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 855 · 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 7 cm, 8 cm and 2 cm? (a) No (b) Yes
  2. 2.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  4. 4.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)?
  5. 5.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  6. 6.In triangle ABC, angle A = 86° and angle B = 31°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 99° and angle B = 35°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  10. 10.In triangle ABC, angle A = 22° and angle B = 45°. What is angle C (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  12. 12.In triangle ABC, angle A = 96° and angle B = 22°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 49° and angle B = 20°. What is angle C (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  15. 15.In triangle ABC, angle A = 90° and angle B = 23°. What is angle C (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 32° and angle B = 25°. What is angle C (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  19. 19.The two interior opposite angles of a triangle are 79° and 20°. What is the exterior angle (in degrees)?
  20. 20.In triangle ABC, angle A = 55° and angle B = 21°. What is angle C (in degrees)?
  21. 21.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  23. 23.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 39° and angle B = 34°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  27. 27.In triangle ABC, angle A = 88° and angle B = 61°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 81° and angle B = 27°. What is angle C (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 55° and 25°. What is the exterior angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 46° and angle B = 95°. What is angle C (in degrees)?
  32. 32.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  33. 33.In triangle ABC, angle A = 55° and angle B = 101°. What is angle C (in degrees)?
  34. 34.Can a triangle have sides of 4 cm, 2 cm and 9 cm? (a) No (b) Yes
  35. 35.The two interior opposite angles of a triangle are 72° and 73°. What is the exterior angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  37. 37.An exterior angle of a triangle is 52°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 41° and 61°. What is the exterior angle (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 51° and 46°. What is the exterior angle (in degrees)?
  40. 40.In triangle ABC, angle A = 67° and angle B = 74°. What is angle C (in degrees)?

Answer key

  1. Yes
  2. 100
  3. 100
  4. 24
  5. 39
  6. 63
  7. 69
  8. 46
  9. 72
  10. 113
  11. 26
  12. 62
  13. 111
  14. 39
  15. 67
  16. 71
  17. 123
  18. 5
  19. 99
  20. 104
  21. 44
  22. 25
  23. 60
  24. 107
  25. 59
  26. 60
  27. 31
  28. 72
  29. 80
  30. 11
  31. 39
  32. 27
  33. 24
  34. No
  35. 145
  36. 47
  37. 26
  38. 102
  39. 97
  40. 39

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