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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 50 · 40 sums
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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 = 59° and angle B = 96°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  5. 5.Can a triangle have sides of 3 cm, 12 cm and 12 cm? (a) Yes (b) No
  6. 6.In triangle ABC, angle A = 25° and angle B = 47°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 22° and angle B = 112°. What is angle C (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 46°. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 37° and angle B = 46°. What is angle C (in degrees)?
  11. 11.In triangle ABC, angle A = 70° and angle B = 26°. What is angle C (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 48° and 41°. What is the exterior angle (in degrees)?
  14. 14.In triangle ABC, angle A = 72° and angle B = 46°. What is angle C (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  16. 16.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)?
  17. 17.An exterior angle of a triangle is 137°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 70° and 52°. What is the exterior angle (in degrees)?
  19. 19.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  21. 21.Can a triangle have sides of 10 cm, 7 cm and 6 cm? (a) No (b) Yes
  22. 22.An exterior angle of a triangle is 62°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  23. 23.In triangle ABC, angle A = 65° and angle B = 32°. What is angle C (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  25. 25.An exterior angle of a triangle is 125°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  27. 27.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  28. 28.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  30. 30.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)?
  31. 31.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)?
  32. 32.In triangle ABC, angle A = 51° and angle B = 25°. What is angle C (in degrees)?
  33. 33.The two shorter sides of a right-angled triangle are 36 cm and 15 cm. How long is the longest side (in cm)?
  34. 34.In triangle ABC, angle A = 42° and angle B = 41°. What is angle C (in degrees)?
  35. 35.Can a triangle have sides of 4 cm, 6 cm and 3 cm? (a) No (b) Yes
  36. 36.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  37. 37.The two interior opposite angles of a triangle are 77° and 57°. What is the exterior angle (in degrees)?
  38. 38.In triangle ABC, angle A = 67° and angle B = 58°. What is angle C (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 35°. What is the third angle (in degrees)?

Answer key

  1. 25
  2. 100
  3. 32
  4. 14
  5. Yes
  6. 108
  7. 46
  8. 44
  9. 45
  10. 97
  11. 84
  12. 24
  13. 89
  14. 62
  15. 24
  16. 8
  17. 65
  18. 122
  19. 20
  20. 43
  21. Yes
  22. 28
  23. 83
  24. 45
  25. 56
  26. 71
  27. 12
  28. 34
  29. 36
  30. 15
  31. 7
  32. 104
  33. 39
  34. 97
  35. Yes
  36. 53
  37. 134
  38. 55
  39. 90
  40. 55

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