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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 183 · 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 = 64° and angle B = 28°. What is angle C (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 17°. What is the third angle (in degrees)?
  4. 4.Can a triangle have sides of 12 cm, 8 cm and 20 cm? (a) Yes (b) No
  5. 5.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)?
  6. 6.Can a triangle have sides of 3 cm, 8 cm and 15 cm? (a) Yes (b) No
  7. 7.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 44° each. What is the third angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  10. 10.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  11. 11.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  12. 12.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 69°. What is the third angle (in degrees)?
  15. 15.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  16. 16.In triangle ABC, angle A = 41° and angle B = 24°. What is angle C (in degrees)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  18. 18.Can a triangle have sides of 6 cm, 6 cm and 1 cm? (a) No (b) Yes
  19. 19.Can a triangle have sides of 6 cm, 11 cm and 4 cm? (a) Yes (b) No
  20. 20.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 11 cm, 5 cm and 7 cm? (a) Yes (b) No
  23. 23.In triangle ABC, angle A = 95° and angle B = 42°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 102°. What is each of the other two angles (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 48° and 42°. What is the exterior angle (in degrees)?
  30. 30.Can a triangle have sides of 17 cm, 6 cm and 10 cm? (a) Yes (b) No
  31. 31.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  32. 32.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 62° each. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  35. 35.Can a triangle have sides of 7 cm, 5 cm and 6 cm? (a) Yes (b) No
  36. 36.In an isosceles triangle, the angle between the two equal sides is 74°. What is each of the other two angles (in degrees)?
  37. 37.In triangle ABC, angle A = 56° and angle B = 87°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  40. 40.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)?

Answer key

  1. 88
  2. 59
  3. 73
  4. No
  5. 7
  6. No
  7. 100
  8. 92
  9. 20
  10. 20
  11. 36
  12. 49
  13. 72
  14. 21
  15. 8
  16. 115
  17. 59
  18. Yes
  19. No
  20. 48
  21. 44
  22. Yes
  23. 43
  24. 36
  25. 45
  26. 39
  27. 70
  28. 68
  29. 90
  30. No
  31. 31
  32. 55
  33. 56
  34. 65
  35. Yes
  36. 53
  37. 37
  38. 90
  39. 10
  40. 9

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