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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 490 · 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 = 61°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 5 cm, 8 cm and 10 cm? (a) No (b) Yes
  7. 7.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  8. 8.An exterior angle of a triangle is 63°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 73° and angle B = 69°. What is angle C (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 52° and 61°. What is the exterior angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 28° and 40°. What is the exterior angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 31° and 43°. What is the exterior angle (in degrees)?
  15. 15.The two interior opposite angles of a triangle are 58° and 34°. What is the exterior angle (in degrees)?
  16. 16.In an isosceles triangle, the angle between the two equal sides is 150°. What is each of the other two angles (in degrees)?
  17. 17.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 62°. What is the other one (in degrees)?
  18. 18.An exterior angle of a triangle is 71°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  19. 19.In triangle ABC, angle A = 95° and angle B = 39°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  21. 21.In triangle ABC, angle A = 38° and angle B = 95°. What is angle C (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 128°. What is each of the other two angles (in degrees)?
  23. 23.In triangle ABC, angle A = 90° and angle B = 41°. What is angle C (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  25. 25.In triangle ABC, angle A = 92° and angle B = 30°. What is angle C (in degrees)?
  26. 26.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)?
  27. 27.The two interior opposite angles of a triangle are 60° and 43°. What is the exterior angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 77°. What is the third angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  31. 31.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  33. 33.Can a triangle have sides of 12 cm, 20 cm and 10 cm? (a) Yes (b) No
  34. 34.The two interior opposite angles of a triangle are 50° and 69°. What is the exterior angle (in degrees)?
  35. 35.In triangle ABC, angle A = 27° and angle B = 98°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 10 cm, 8 cm and 11 cm? (a) Yes (b) No
  37. 37.The two interior opposite angles of a triangle are 74° and 71°. What is the exterior angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 47° each. What is the third angle (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 83° and angle B = 51°. What is angle C (in degrees)?

Answer key

  1. 92
  2. 20
  3. 36
  4. 54
  5. 84
  6. Yes
  7. 70
  8. 27
  9. 48
  10. 38
  11. 12
  12. 113
  13. 68
  14. 74
  15. 92
  16. 15
  17. 56
  18. 34
  19. 46
  20. 10
  21. 47
  22. 26
  23. 49
  24. 25
  25. 58
  26. 7
  27. 103
  28. 13
  29. 37
  30. 13
  31. 35
  32. 20
  33. Yes
  34. 119
  35. 55
  36. Yes
  37. 145
  38. 86
  39. 46
  40. 46

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