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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 832 · 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 : 3. What is the smallest angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  3. 3.The two interior opposite angles of a triangle are 61° and 37°. What is the exterior angle (in degrees)?
  4. 4.Can a triangle have sides of 6 cm, 6 cm and 6 cm? (a) No (b) Yes
  5. 5.The two interior opposite angles of a triangle are 69° and 77°. What is the exterior angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  7. 7.Can a triangle have sides of 8 cm, 14 cm and 3 cm? (a) Yes (b) No
  8. 8.Can a triangle have sides of 14 cm, 7 cm and 6 cm? (a) No (b) Yes
  9. 9.Can a triangle have sides of 18 cm, 8 cm and 9 cm? (a) No (b) Yes
  10. 10.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  11. 11.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  12. 12.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  13. 13.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  14. 14.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  15. 15.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 40°. What is each of the other two angles (in degrees)?
  21. 21.Can a triangle have sides of 17 cm, 7 cm and 7 cm? (a) Yes (b) No
  22. 22.In triangle ABC, angle A = 82° and angle B = 54°. What is angle C (in degrees)?
  23. 23.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  24. 24.Can a triangle have sides of 12 cm, 6 cm and 3 cm? (a) Yes (b) No
  25. 25.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  27. 27.In triangle ABC, angle A = 80° and angle B = 21°. What is angle C (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  31. 31.Can a triangle have sides of 4 cm, 14 cm and 12 cm? (a) No (b) Yes
  32. 32.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 57° and 36°. What is the exterior angle (in degrees)?
  35. 35.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  36. 36.Can a triangle have sides of 7 cm, 12 cm and 10 cm? (a) Yes (b) No
  37. 37.An exterior angle of a triangle is 54°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  38. 38.Can a triangle have sides of 16 cm, 11 cm and 3 cm? (a) No (b) Yes
  39. 39.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 8 cm, 12 cm and 5 cm? (a) Yes (b) No

Answer key

  1. 30
  2. 36
  3. 98
  4. Yes
  5. 146
  6. 120
  7. No
  8. No
  9. No
  10. 24
  11. 62
  12. 76
  13. 80
  14. 12
  15. 25
  16. 25
  17. 72
  18. 75
  19. 28
  20. 70
  21. No
  22. 44
  23. 20
  24. No
  25. 71
  26. 57
  27. 79
  28. 12
  29. 50
  30. 25
  31. Yes
  32. 74
  33. 42
  34. 93
  35. 79
  36. Yes
  37. 31
  38. No
  39. 66
  40. Yes

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