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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 720 · 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 = 52° and angle B = 45°. What is angle C (in degrees)?
  2. 2.In triangle ABC, angle A = 73° and angle B = 63°. What is angle C (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  5. 5.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  6. 6.In triangle ABC, angle A = 72° and angle B = 20°. What is angle C (in degrees)?
  7. 7.The two interior opposite angles of a triangle are 44° and 62°. What is the exterior angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  14. 14.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  15. 15.An exterior angle of a triangle is 139°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  17. 17.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  19. 19.In triangle ABC, angle A = 31° and angle B = 60°. What is angle C (in degrees)?
  20. 20.An exterior angle of a triangle is 141°. One of its two interior opposite angles is 64°. What is the other one (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  22. 22.Can a triangle have sides of 11 cm, 18 cm and 8 cm? (a) No (b) Yes
  23. 23.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  24. 24.The two interior opposite angles of a triangle are 78° and 32°. What is the exterior angle (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  26. 26.The two interior opposite angles of a triangle are 46° and 39°. What is the exterior angle (in degrees)?
  27. 27.An exterior angle of a triangle is 111°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  28. 28.In an isosceles triangle, the two equal angles are 46° each. What is the third angle (in degrees)?
  29. 29.An exterior angle of a triangle is 141°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  30. 30.Can a triangle have sides of 2 cm, 12 cm and 17 cm? (a) No (b) Yes
  31. 31.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)?
  32. 32.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  33. 33.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  34. 34.An exterior angle of a triangle is 154°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 8 cm and 6 cm. How long is the longest side (in cm)?
  36. 36.In triangle ABC, angle A = 28° and angle B = 95°. What is angle C (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 51° and 74°. What is the exterior angle (in degrees)?
  38. 38.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  39. 39.In triangle ABC, angle A = 85° and angle B = 62°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?

Answer key

  1. 83
  2. 44
  3. 36
  4. 40
  5. 39
  6. 88
  7. 106
  8. 68
  9. 67
  10. 74
  11. 76
  12. 53
  13. 100
  14. 120
  15. 74
  16. 36
  17. 24
  18. 36
  19. 89
  20. 77
  21. 58
  22. Yes
  23. 90
  24. 110
  25. 20
  26. 85
  27. 74
  28. 88
  29. 65
  30. No
  31. 24
  32. 124
  33. 20
  34. 74
  35. 10
  36. 57
  37. 125
  38. 17
  39. 33
  40. 52

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