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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 655 · 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 33°. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 9 cm, 8 cm and 8 cm? (a) Yes (b) No
  3. 3.In triangle ABC, angle A = 34° and angle B = 39°. What is angle C (in degrees)?
  4. 4.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  5. 5.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  6. 6.Can a triangle have sides of 12 cm, 19 cm and 7 cm? (a) Yes (b) No
  7. 7.An exterior angle of a triangle is 80°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  8. 8.Can a triangle have sides of 11 cm, 19 cm and 5 cm? (a) Yes (b) No
  9. 9.The two interior opposite angles of a triangle are 60° and 43°. What is the exterior angle (in degrees)?
  10. 10.Can a triangle have sides of 8 cm, 5 cm and 8 cm? (a) Yes (b) No
  11. 11.The two interior opposite angles of a triangle are 78° and 32°. What is the exterior angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 31° and 59°. What is the exterior angle (in degrees)?
  13. 13.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  14. 14.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  15. 15.An exterior angle of a triangle is 64°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 12 cm and 16 cm. How long is the longest side (in cm)?
  17. 17.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 45° and 21°. What is the exterior angle (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  22. 22.In triangle ABC, angle A = 61° and angle B = 40°. What is angle C (in degrees)?
  23. 23.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  25. 25.In triangle ABC, angle A = 28° and angle B = 94°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  27. 27.The two interior opposite angles of a triangle are 24° and 24°. What is the exterior angle (in degrees)?
  28. 28.Can a triangle have sides of 10 cm, 21 cm and 9 cm? (a) Yes (b) No
  29. 29.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 24° each. What is the third angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  34. 34.Can a triangle have sides of 10 cm, 22 cm and 11 cm? (a) Yes (b) No
  35. 35.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 6 cm, 9 cm and 2 cm? (a) Yes (b) No
  37. 37.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  39. 39.The longest side of a right-angled triangle is 15 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  40. 40.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?

Answer key

  1. 57
  2. Yes
  3. 107
  4. 8
  5. 72
  6. No
  7. 39
  8. No
  9. 103
  10. Yes
  11. 110
  12. 90
  13. 55
  14. 43
  15. 32
  16. 20
  17. 20
  18. 66
  19. 82
  20. 74
  21. 45
  22. 79
  23. 70
  24. 13
  25. 58
  26. 54
  27. 48
  28. No
  29. 20
  30. 90
  31. 132
  32. 12
  33. 35
  34. No
  35. 98
  36. No
  37. 75
  38. 17
  39. 9
  40. 36

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