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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 422 · 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.Can a triangle have sides of 11 cm, 9 cm and 9 cm? (a) Yes (b) No
  2. 2.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  3. 3.Can a triangle have sides of 2 cm, 7 cm and 7 cm? (a) No (b) Yes
  4. 4.Can a triangle have sides of 6 cm, 6 cm and 1 cm? (a) No (b) Yes
  5. 5.The two interior opposite angles of a triangle are 55° and 45°. What is the exterior angle (in degrees)?
  6. 6.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)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  8. 8.In triangle ABC, angle A = 66° and angle B = 37°. What is angle C (in degrees)?
  9. 9.In triangle ABC, angle A = 72° and angle B = 49°. What is angle C (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 46° and 48°. What is the exterior angle (in degrees)?
  11. 11.In triangle ABC, angle A = 85° and angle B = 31°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 9 cm, 11 cm and 20 cm? (a) No (b) Yes
  13. 13.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  14. 14.Can a triangle have sides of 9 cm, 10 cm and 3 cm? (a) Yes (b) No
  15. 15.In an isosceles triangle, the angle between the two equal sides is 50°. What is each of the other two angles (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  17. 17.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)?
  18. 18.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  19. 19.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  20. 20.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  21. 21.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)?
  22. 22.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  23. 23.Can a triangle have sides of 9 cm, 3 cm and 8 cm? (a) No (b) Yes
  24. 24.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  25. 25.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 15 cm, 4 cm and 9 cm? (a) Yes (b) No
  27. 27.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  28. 28.In triangle ABC, angle A = 59° and angle B = 43°. What is angle C (in degrees)?
  29. 29.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  30. 30.In an isosceles triangle, the angle between the two equal sides is 134°. What is each of the other two angles (in degrees)?
  31. 31.In triangle ABC, angle A = 24° and angle B = 54°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 73° and angle B = 46°. What is angle C (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  34. 34.In triangle ABC, angle A = 45° and angle B = 109°. What is angle C (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 31° and 64°. What is the exterior angle (in degrees)?
  36. 36.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  37. 37.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  38. 38.In triangle ABC, angle A = 52° and angle B = 82°. What is angle C (in degrees)?
  39. 39.An exterior angle of a triangle is 135°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  40. 40.Can a triangle have sides of 11 cm, 2 cm and 10 cm? (a) No (b) Yes

Answer key

  1. Yes
  2. 66
  3. Yes
  4. Yes
  5. 100
  6. 24
  7. 57
  8. 77
  9. 59
  10. 94
  11. 64
  12. No
  13. 65
  14. Yes
  15. 65
  16. 26
  17. 36
  18. 72
  19. 25
  20. 9
  21. 24
  22. 56
  23. Yes
  24. 25
  25. 40
  26. No
  27. 37
  28. 78
  29. 70
  30. 23
  31. 102
  32. 61
  33. 120
  34. 26
  35. 95
  36. 31
  37. 22
  38. 46
  39. 65
  40. Yes

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