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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 507 · 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 a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  3. 3.In triangle ABC, angle A = 84° and angle B = 73°. What is angle C (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 60° and 52°. What is the exterior angle (in degrees)?
  6. 6.Can a triangle have sides of 5 cm, 21 cm and 11 cm? (a) Yes (b) No
  7. 7.The two interior opposite angles of a triangle are 22° and 32°. What is the exterior angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 67° and angle B = 62°. What is angle C (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 60° each. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 32° and 34°. What is the exterior angle (in degrees)?
  13. 13.Can a triangle have sides of 2 cm, 18 cm and 11 cm? (a) Yes (b) No
  14. 14.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  15. 15.In triangle ABC, angle A = 28° and angle B = 89°. What is angle C (in degrees)?
  16. 16.The two interior opposite angles of a triangle are 37° and 41°. What is the exterior angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  20. 20.Can a triangle have sides of 2 cm, 3 cm and 3 cm? (a) Yes (b) No
  21. 21.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  22. 22.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)?
  23. 23.In an isosceles triangle, the two equal angles are 85° each. What is the third angle (in degrees)?
  24. 24.In triangle ABC, angle A = 42° and angle B = 67°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 72° and angle B = 20°. What is angle C (in degrees)?
  26. 26.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)?
  27. 27.Can a triangle have sides of 12 cm, 11 cm and 2 cm? (a) No (b) Yes
  28. 28.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 67° and angle B = 71°. What is angle C (in degrees)?
  31. 31.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)?
  32. 32.In triangle ABC, angle A = 47° and angle B = 103°. What is angle C (in degrees)?
  33. 33.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  34. 34.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  35. 35.Can a triangle have sides of 25 cm, 8 cm and 12 cm? (a) Yes (b) No
  36. 36.Can a triangle have sides of 8 cm, 19 cm and 12 cm? (a) Yes (b) No
  37. 37.In an isosceles triangle, the two equal angles are 82° each. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 9 cm, 4 cm and 10 cm? (a) No (b) Yes
  39. 39.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?

Answer key

  1. 79
  2. 54
  3. 23
  4. 41
  5. 112
  6. No
  7. 54
  8. 50
  9. 51
  10. 60
  11. 20
  12. 66
  13. No
  14. 62
  15. 63
  16. 78
  17. 36
  18. 90
  19. 50
  20. Yes
  21. 45
  22. 10
  23. 10
  24. 71
  25. 88
  26. 24
  27. Yes
  28. 43
  29. 82
  30. 42
  31. 7
  32. 30
  33. 28
  34. 72
  35. No
  36. Yes
  37. 16
  38. Yes
  39. 130
  40. 48

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