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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 85 · 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.

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  1. 1.In triangle ABC, angle A = 27° and angle B = 130°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 79° and angle B = 44°. What is angle C (in degrees)?
  3. 3.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  5. 5.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  8. 8.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 60° and angle B = 84°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 37° and angle B = 110°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 4 cm, 14 cm and 9 cm? (a) Yes (b) No
  13. 13.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  15. 15.Can a triangle have sides of 8 cm, 8 cm and 18 cm? (a) Yes (b) No
  16. 16.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  17. 17.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  18. 18.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  19. 19.In triangle ABC, angle A = 20° and angle B = 127°. What is angle C (in degrees)?
  20. 20.Can a triangle have sides of 6 cm, 5 cm and 9 cm? (a) Yes (b) No
  21. 21.Can a triangle have sides of 2 cm, 2 cm and 1 cm? (a) Yes (b) No
  22. 22.In triangle ABC, angle A = 28° and angle B = 62°. What is angle C (in degrees)?
  23. 23.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  24. 24.Can a triangle have sides of 3 cm, 7 cm and 12 cm? (a) Yes (b) No
  25. 25.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  26. 26.In triangle ABC, angle A = 27° and angle B = 37°. What is angle C (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  28. 28.Can a triangle have sides of 7 cm, 8 cm and 7 cm? (a) No (b) Yes
  29. 29.In triangle ABC, angle A = 49° and angle B = 109°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 54° and angle B = 92°. What is angle C (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 39° each. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 85° and angle B = 63°. What is angle C (in degrees)?
  33. 33.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)?
  34. 34.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 72° and angle B = 30°. What is angle C (in degrees)?
  39. 39.Can a triangle have sides of 8 cm, 6 cm and 16 cm? (a) Yes (b) No
  40. 40.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?

Answer key

  1. 23
  2. 57
  3. 36
  4. 13
  5. 61
  6. 49
  7. 38
  8. 51
  9. 54
  10. 36
  11. 33
  12. No
  13. 72
  14. 54
  15. No
  16. 17
  17. 39
  18. 36
  19. 33
  20. Yes
  21. Yes
  22. 90
  23. 48
  24. No
  25. 46
  26. 116
  27. 26
  28. Yes
  29. 22
  30. 34
  31. 102
  32. 32
  33. 24
  34. 39
  35. 66
  36. 45
  37. 33
  38. 78
  39. No
  40. 25

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