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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 87 · 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 = 75° and angle B = 43°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 107°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 47° and 20°. What is the exterior angle (in degrees)?
  6. 6.In triangle ABC, angle A = 75° and angle B = 32°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  9. 9.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  10. 10.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  12. 12.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  13. 13.Can a triangle have sides of 17 cm, 7 cm and 7 cm? (a) No (b) Yes
  14. 14.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  15. 15.An exterior angle of a triangle is 156°. One of its two interior opposite angles is 78°. What is the other one (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 34°. What is each of the other two angles (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  19. 19.Can a triangle have sides of 10 cm, 4 cm and 13 cm? (a) No (b) Yes
  20. 20.Can a triangle have sides of 2 cm, 9 cm and 8 cm? (a) Yes (b) No
  21. 21.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 18 cm, 6 cm and 12 cm? (a) Yes (b) No
  23. 23.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  24. 24.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  25. 25.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 12 cm, 24 cm and 10 cm? (a) Yes (b) No
  28. 28.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  29. 29.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)?
  30. 30.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)?
  31. 31.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 21° and 73°. What is the exterior angle (in degrees)?
  34. 34.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  35. 35.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (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 shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  38. 38.In an isosceles triangle, the angle between the two equal sides is 82°. What is each of the other two angles (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  40. 40.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?

Answer key

  1. 62
  2. 90
  3. 52
  4. 20
  5. 67
  6. 73
  7. 90
  8. 27
  9. 39
  10. 45
  11. 33
  12. 90
  13. No
  14. 132
  15. 78
  16. 46
  17. 73
  18. 65
  19. Yes
  20. Yes
  21. 43
  22. No
  23. 3
  24. 5
  25. 69
  26. 20
  27. No
  28. 66
  29. 24
  30. 7
  31. 18
  32. 44
  33. 94
  34. 37
  35. 70
  36. 72
  37. 25
  38. 49
  39. 50
  40. 36

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