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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 886 · 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 = 80° and angle B = 55°. What is angle C (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 60° and 52°. What is the exterior angle (in degrees)?
  3. 3.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  4. 4.The two interior opposite angles of a triangle are 78° and 55°. What is the exterior angle (in degrees)?
  5. 5.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)?
  6. 6.The two interior opposite angles of a triangle are 58° and 58°. What is the exterior angle (in degrees)?
  7. 7.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  8. 8.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 5 cm, 5 cm and 11 cm? (a) No (b) Yes
  11. 11.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 154°. What is each of the other two angles (in degrees)?
  13. 13.Can a triangle have sides of 5 cm, 6 cm and 6 cm? (a) Yes (b) No
  14. 14.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 33° and 74°. What is the exterior 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 1 : 2 : 3. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  21. 21.In triangle ABC, angle A = 75° and angle B = 23°. What is angle C (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 67° and angle B = 81°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 95° and angle B = 42°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 8 cm, 20 cm and 9 cm? (a) Yes (b) No
  31. 31.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  32. 32.In triangle ABC, angle A = 92° and angle B = 57°. What is angle C (in degrees)?
  33. 33.Can a triangle have sides of 1 cm, 5 cm and 5 cm? (a) No (b) Yes
  34. 34.Can a triangle have sides of 7 cm, 8 cm and 2 cm? (a) No (b) Yes
  35. 35.The two interior opposite angles of a triangle are 33° and 64°. What is the exterior angle (in degrees)?
  36. 36.The two interior opposite angles of a triangle are 76° and 67°. What is the exterior angle (in degrees)?
  37. 37.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  38. 38.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  39. 39.In triangle ABC, angle A = 26° and angle B = 89°. What is angle C (in degrees)?
  40. 40.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?

Answer key

  1. 45
  2. 112
  3. 5
  4. 133
  5. 24
  6. 116
  7. 54
  8. 36
  9. 22
  10. No
  11. 10
  12. 13
  13. Yes
  14. 47
  15. 69
  16. 22
  17. 107
  18. 90
  19. 30
  20. 78
  21. 82
  22. 80
  23. 32
  24. 26
  25. 61
  26. 72
  27. 62
  28. 42
  29. 43
  30. No
  31. 78
  32. 31
  33. Yes
  34. Yes
  35. 97
  36. 143
  37. 25
  38. 6
  39. 65
  40. 48

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