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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 744 · 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 = 81° and angle B = 75°. What is angle C (in degrees)?
  2. 2.Can a triangle have sides of 20 cm, 5 cm and 10 cm? (a) No (b) Yes
  3. 3.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  6. 6.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)?
  7. 7.An exterior angle of a triangle is 53°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  9. 9.The two interior opposite angles of a triangle are 70° and 21°. What is the exterior angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 21° and 41°. What is the exterior angle (in degrees)?
  11. 11.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 79° and 43°. What is the exterior angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  14. 14.The two interior opposite angles of a triangle are 54° and 33°. What is the exterior angle (in degrees)?
  15. 15.In triangle ABC, angle A = 35° and angle B = 59°. What is angle C (in degrees)?
  16. 16.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  17. 17.In triangle ABC, angle A = 27° and angle B = 106°. What is angle C (in degrees)?
  18. 18.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 80°. What is the third angle (in degrees)?
  22. 22.In triangle ABC, angle A = 79° and angle B = 26°. What is angle C (in degrees)?
  23. 23.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  24. 24.Can a triangle have sides of 4 cm, 10 cm and 11 cm? (a) Yes (b) No
  25. 25.Can a triangle have sides of 8 cm, 4 cm and 10 cm? (a) No (b) Yes
  26. 26.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  27. 27.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  28. 28.An exterior angle of a triangle is 69°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  29. 29.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  30. 30.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  33. 33.In triangle ABC, angle A = 23° and angle B = 56°. What is angle C (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  36. 36.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 26°. What is the third angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  40. 40.In triangle ABC, angle A = 77° and angle B = 29°. What is angle C (in degrees)?

Answer key

  1. 24
  2. No
  3. 75
  4. 70
  5. 72
  6. 8
  7. 32
  8. 14
  9. 91
  10. 62
  11. 45
  12. 122
  13. 90
  14. 87
  15. 86
  16. 15
  17. 47
  18. 84
  19. 40
  20. 57
  21. 10
  22. 75
  23. 12
  24. Yes
  25. Yes
  26. 5
  27. 20
  28. 20
  29. 48
  30. 78
  31. 63
  32. 10
  33. 101
  34. 14
  35. 20
  36. 90
  37. 64
  38. 80
  39. 30
  40. 74

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