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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 801 · 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 a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 72° and angle B = 41°. What is angle C (in degrees)?
  6. 6.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  7. 7.In triangle ABC, angle A = 84° and angle B = 46°. What is angle C (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  9. 9.An exterior angle of a triangle is 123°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  10. 10.Can a triangle have sides of 12 cm, 8 cm and 18 cm? (a) Yes (b) No
  11. 11.In an isosceles triangle, the angle between the two equal sides is 22°. What is each of the other two angles (in degrees)?
  12. 12.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  13. 13.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  14. 14.In triangle ABC, angle A = 37° and angle B = 55°. What is angle C (in degrees)?
  15. 15.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  16. 16.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  17. 17.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 55° and angle B = 63°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?
  21. 21.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  22. 22.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  25. 25.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 41°. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 10 cm, 10 cm and 2 cm? (a) No (b) Yes
  30. 30.In triangle ABC, angle A = 92° and angle B = 60°. What is angle C (in degrees)?
  31. 31.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)?
  32. 32.Can a triangle have sides of 8 cm, 16 cm and 4 cm? (a) Yes (b) No
  33. 33.In triangle ABC, angle A = 33° and angle B = 82°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 32° and 35°. What is the exterior angle (in degrees)?
  36. 36.Can a triangle have sides of 3 cm, 8 cm and 11 cm? (a) Yes (b) No
  37. 37.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)?
  38. 38.The two shorter sides of a right-angled triangle are 18 cm and 24 cm. How long is the longest side (in cm)?
  39. 39.In triangle ABC, angle A = 36° and angle B = 57°. What is angle C (in degrees)?
  40. 40.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?

Answer key

  1. 68
  2. 37
  3. 23
  4. 20
  5. 67
  6. 40
  7. 50
  8. 51
  9. 57
  10. Yes
  11. 79
  12. 45
  13. 37
  14. 88
  15. 10
  16. 26
  17. 56
  18. 25
  19. 62
  20. 47
  21. 70
  22. 29
  23. 80
  24. 120
  25. 67
  26. 35
  27. 64
  28. 49
  29. Yes
  30. 28
  31. 5
  32. No
  33. 65
  34. 14
  35. 67
  36. No
  37. 4
  38. 30
  39. 87
  40. 84

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