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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 64 · 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 = 71° and angle B = 29°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 4 cm, 3 cm and 3 cm? (a) No (b) Yes
  3. 3.In triangle ABC, angle A = 41° and angle B = 42°. What is angle C (in degrees)?
  4. 4.In triangle ABC, angle A = 20° and angle B = 81°. What is angle C (in degrees)?
  5. 5.Can a triangle have sides of 12 cm, 8 cm and 14 cm? (a) No (b) Yes
  6. 6.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  8. 8.An exterior angle of a triangle is 146°. One of its two interior opposite angles is 71°. What is the other one (in degrees)?
  9. 9.Can a triangle have sides of 6 cm, 2 cm and 5 cm? (a) Yes (b) No
  10. 10.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  11. 11.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 42° and 52°. What is the exterior angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  14. 14.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  15. 15.In triangle ABC, angle A = 89° and angle B = 47°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 78° and angle B = 46°. What is angle C (in degrees)?
  17. 17.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  18. 18.Can a triangle have sides of 3 cm, 10 cm and 10 cm? (a) Yes (b) No
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 53° and 24°. What is the exterior angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 36° and angle B = 102°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 42° and angle B = 114°. What is angle C (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 3 cm, 5 cm and 8 cm? (a) Yes (b) No
  32. 32.Can a triangle have sides of 11 cm, 11 cm and 5 cm? (a) Yes (b) No
  33. 33.In triangle ABC, angle A = 94° and angle B = 41°. What is angle C (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 54° each. What is the third angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  36. 36.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  37. 37.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  38. 38.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  39. 39.In an isosceles triangle, the angle between the two equal sides is 96°. What is each of the other two angles (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?

Answer key

  1. 80
  2. Yes
  3. 97
  4. 79
  5. Yes
  6. 44
  7. 25
  8. 75
  9. Yes
  10. 36
  11. 70
  12. 94
  13. 13
  14. 64
  15. 44
  16. 56
  17. 61
  18. Yes
  19. 90
  20. 77
  21. 47
  22. 42
  23. 20
  24. 11
  25. 90
  26. 122
  27. 77
  28. 84
  29. 24
  30. 41
  31. No
  32. Yes
  33. 45
  34. 72
  35. 10
  36. 18
  37. 32
  38. 75
  39. 42
  40. 37

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