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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 769 · 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.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  2. 2.In triangle ABC, angle A = 92° and angle B = 44°. What is angle C (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  4. 4.Can a triangle have sides of 9 cm, 7 cm and 13 cm? (a) No (b) Yes
  5. 5.In triangle ABC, angle A = 48° and angle B = 83°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 50° and angle B = 104°. What is angle C (in degrees)?
  10. 10.In triangle ABC, angle A = 73° and angle B = 24°. What is angle C (in degrees)?
  11. 11.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  14. 14.In triangle ABC, angle A = 97° and angle B = 55°. What is angle C (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  16. 16.In triangle ABC, angle A = 30° and angle B = 25°. What is angle C (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  19. 19.Can a triangle have sides of 3 cm, 4 cm and 7 cm? (a) No (b) Yes
  20. 20.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  21. 21.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 42° and angle B = 46°. What is angle C (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 58° and 71°. What is the exterior angle (in degrees)?
  24. 24.Can a triangle have sides of 4 cm, 12 cm and 6 cm? (a) Yes (b) No
  25. 25.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  26. 26.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  27. 27.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  30. 30.In triangle ABC, angle A = 62° and angle B = 95°. What is angle C (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 51° and 59°. What is the exterior angle (in degrees)?
  32. 32.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  33. 33.Can a triangle have sides of 15 cm, 7 cm and 10 cm? (a) No (b) Yes
  34. 34.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 90° and angle B = 25°. What is angle C (in degrees)?
  36. 36.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 58° and 36°. What is the exterior angle (in degrees)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  39. 39.The two interior opposite angles of a triangle are 48° and 64°. What is the exterior angle (in degrees)?
  40. 40.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?

Answer key

  1. 36
  2. 44
  3. 74
  4. Yes
  5. 49
  6. 124
  7. 64
  8. 76
  9. 26
  10. 83
  11. 49
  12. 16
  13. 20
  14. 28
  15. 48
  16. 125
  17. 30
  18. 30
  19. No
  20. 15
  21. 73
  22. 92
  23. 129
  24. No
  25. 20
  26. 4
  27. 20
  28. 140
  29. 20
  30. 23
  31. 110
  32. 18
  33. Yes
  34. 36
  35. 65
  36. 72
  37. 94
  38. 60
  39. 112
  40. 60

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