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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 883 · 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.The two interior opposite angles of a triangle are 41° and 41°. What is the exterior angle (in degrees)?
  2. 2.Can a triangle have sides of 11 cm, 18 cm and 4 cm? (a) No (b) Yes
  3. 3.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  4. 4.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  5. 5.Can a triangle have sides of 12 cm, 4 cm and 9 cm? (a) No (b) Yes
  6. 6.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 46° and angle B = 81°. What is angle C (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  9. 9.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)?
  10. 10.The two interior opposite angles of a triangle are 65° and 71°. What is the exterior angle (in degrees)?
  11. 11.Can a triangle have sides of 13 cm, 6 cm and 7 cm? (a) Yes (b) No
  12. 12.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  13. 13.In triangle ABC, angle A = 82° and angle B = 64°. What is angle C (in degrees)?
  14. 14.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  16. 16.Can a triangle have sides of 14 cm, 9 cm and 5 cm? (a) No (b) Yes
  17. 17.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)?
  18. 18.In triangle ABC, angle A = 46° and angle B = 29°. What is angle C (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 50° and 60°. What is the exterior angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  21. 21.In an isosceles triangle, the two equal angles are 75° each. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  23. 23.In triangle ABC, angle A = 80° and angle B = 49°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 33°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 81° and angle B = 73°. What is angle C (in degrees)?
  27. 27.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 35° each. What is the third angle (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 116°. What is each of the other two angles (in degrees)?
  31. 31.Can a triangle have sides of 7 cm, 11 cm and 22 cm? (a) No (b) Yes
  32. 32.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  33. 33.Can a triangle have sides of 10 cm, 18 cm and 3 cm? (a) No (b) Yes
  34. 34.Can a triangle have sides of 9 cm, 23 cm and 11 cm? (a) Yes (b) No
  35. 35.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  36. 36.Can a triangle have sides of 12 cm, 10 cm and 9 cm? (a) No (b) Yes
  37. 37.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?

Answer key

  1. 82
  2. No
  3. 36
  4. 24
  5. Yes
  6. 84
  7. 53
  8. 90
  9. 7
  10. 136
  11. No
  12. 33
  13. 34
  14. 75
  15. 20
  16. No
  17. 12
  18. 105
  19. 110
  20. 42
  21. 30
  22. 20
  23. 51
  24. 72
  25. 57
  26. 26
  27. 54
  28. 110
  29. 90
  30. 32
  31. No
  32. 11
  33. No
  34. No
  35. 75
  36. Yes
  37. 72
  38. 37
  39. 30
  40. 73

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