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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 774 · 40 sums
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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 = 57° and angle B = 79°. What is angle C (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  3. 3.Can a triangle have sides of 22 cm, 10 cm and 10 cm? (a) Yes (b) No
  4. 4.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  5. 5.In triangle ABC, angle A = 72° and angle B = 55°. What is angle C (in degrees)?
  6. 6.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  7. 7.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  8. 8.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  10. 10.Can a triangle have sides of 3 cm, 2 cm and 3 cm? (a) Yes (b) No
  11. 11.An exterior angle of a triangle is 47°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  12. 12.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  13. 13.In triangle ABC, angle A = 79° and angle B = 38°. What is angle C (in degrees)?
  14. 14.In an isosceles triangle, the angle between the two equal sides is 84°. What is each of the other two angles (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 28° and angle B = 105°. What is angle C (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  20. 20.The two interior opposite angles of a triangle are 38° and 44°. What is the exterior angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  22. 22.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  24. 24.The two interior opposite angles of a triangle are 40° and 70°. What is the exterior angle (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 37° and 44°. What is the exterior angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  27. 27.In triangle ABC, angle A = 28° and angle B = 121°. What is angle C (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 35° and 79°. What is the exterior angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 26° and 40°. What is the exterior angle (in degrees)?
  30. 30.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)?
  31. 31.Can a triangle have sides of 21 cm, 10 cm and 6 cm? (a) No (b) Yes
  32. 32.In triangle ABC, angle A = 85° and angle B = 20°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  36. 36.The two interior opposite angles of a triangle are 20° and 53°. What is the exterior angle (in degrees)?
  37. 37.Can a triangle have sides of 11 cm, 9 cm and 3 cm? (a) No (b) Yes
  38. 38.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  40. 40.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 35°. What is the other one (in degrees)?

Answer key

  1. 44
  2. 64
  3. No
  4. 50
  5. 53
  6. 58
  7. 15
  8. 36
  9. 100
  10. Yes
  11. 25
  12. 54
  13. 63
  14. 48
  15. 37
  16. 72
  17. 47
  18. 45
  19. 31
  20. 82
  21. 60
  22. 37
  23. 20
  24. 110
  25. 81
  26. 72
  27. 31
  28. 114
  29. 66
  30. 15
  31. No
  32. 75
  33. 36
  34. 74
  35. 25
  36. 73
  37. Yes
  38. 44
  39. 92
  40. 35

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