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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 731 · 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 = 75° and angle B = 26°. What is angle C (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 27° and 76°. What is the exterior angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  7. 7.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  8. 8.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  9. 9.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  10. 10.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 50° and 26°. What is the exterior angle (in degrees)?
  14. 14.In triangle ABC, angle A = 40° and angle B = 90°. What is angle C (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  17. 17.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)?
  18. 18.Can a triangle have sides of 6 cm, 6 cm and 11 cm? (a) No (b) Yes
  19. 19.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 23 cm, 7 cm and 12 cm? (a) Yes (b) No
  22. 22.Can a triangle have sides of 10 cm, 6 cm and 20 cm? (a) Yes (b) No
  23. 23.The two interior opposite angles of a triangle are 54° and 70°. What is the exterior angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  25. 25.In triangle ABC, angle A = 50° and angle B = 56°. What is angle C (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 73° each. What is the third angle (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  31. 31.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  32. 32.In triangle ABC, angle A = 85° and angle B = 49°. What is angle C (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  34. 34.Can a triangle have sides of 4 cm, 14 cm and 12 cm? (a) No (b) Yes
  35. 35.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)?
  36. 36.Can a triangle have sides of 9 cm, 5 cm and 12 cm? (a) Yes (b) No
  37. 37.In triangle ABC, angle A = 82° and angle B = 56°. What is angle C (in degrees)?
  38. 38.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?

Answer key

  1. 79
  2. 103
  3. 22
  4. 18
  5. 100
  6. 90
  7. 10
  8. 45
  9. 30
  10. 84
  11. 80
  12. 44
  13. 76
  14. 50
  15. 28
  16. 25
  17. 7
  18. Yes
  19. 48
  20. 118
  21. No
  22. No
  23. 124
  24. 40
  25. 74
  26. 14
  27. 40
  28. 24
  29. 34
  30. 22
  31. 12
  32. 46
  33. 44
  34. Yes
  35. 10
  36. Yes
  37. 42
  38. 75
  39. 69
  40. 76

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