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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 542 · 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.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  5. 5.In triangle ABC, angle A = 39° and angle B = 45°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 29° and angle B = 27°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  9. 9.In triangle ABC, angle A = 82° and angle B = 65°. What is angle C (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  11. 11.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  14. 14.Can a triangle have sides of 10 cm, 8 cm and 22 cm? (a) Yes (b) No
  15. 15.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  17. 17.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  18. 18.In triangle ABC, angle A = 22° and angle B = 40°. What is angle C (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 80° and 70°. What is the exterior angle (in degrees)?
  20. 20.In triangle ABC, angle A = 82° and angle B = 47°. What is angle C (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 9 cm, 6 cm and 9 cm? (a) No (b) Yes
  23. 23.The two interior opposite angles of a triangle are 48° and 54°. What is the exterior angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 65° and 77°. What is the exterior angle (in degrees)?
  25. 25.Can a triangle have sides of 10 cm, 4 cm and 9 cm? (a) No (b) Yes
  26. 26.Can a triangle have sides of 11 cm, 12 cm and 3 cm? (a) No (b) Yes
  27. 27.Can a triangle have sides of 11 cm, 3 cm and 8 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 86° and angle B = 41°. What is angle C (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 31° and angle B = 33°. What is angle C (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 27° and 42°. What is the exterior angle (in degrees)?
  32. 32.An exterior angle of a triangle is 48°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  33. 33.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 90°. What is each of the other two angles (in degrees)?
  37. 37.Can a triangle have sides of 11 cm, 8 cm and 7 cm? (a) No (b) Yes
  38. 38.The two interior opposite angles of a triangle are 43° and 52°. What is the exterior angle (in degrees)?
  39. 39.An exterior angle of a triangle is 138°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  40. 40.In triangle ABC, angle A = 41° and angle B = 111°. What is angle C (in degrees)?

Answer key

  1. 20
  2. 58
  3. 18
  4. 20
  5. 96
  6. 124
  7. 64
  8. 17
  9. 33
  10. 122
  11. 59
  12. 14
  13. 26
  14. No
  15. 53
  16. 45
  17. 16
  18. 118
  19. 150
  20. 51
  21. 72
  22. Yes
  23. 102
  24. 142
  25. Yes
  26. Yes
  27. No
  28. 53
  29. 20
  30. 116
  31. 69
  32. 20
  33. 54
  34. 63
  35. 75
  36. 45
  37. Yes
  38. 95
  39. 61
  40. 28

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