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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 18 · 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 = 25° and angle B = 37°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 156°. What is each of the other two angles (in degrees)?
  4. 4.Can a triangle have sides of 7 cm, 15 cm and 3 cm? (a) Yes (b) No
  5. 5.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  6. 6.In triangle ABC, angle A = 37° and angle B = 71°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 93° and angle B = 55°. What is angle C (in degrees)?
  9. 9.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  10. 10.Can a triangle have sides of 4 cm, 12 cm and 5 cm? (a) No (b) Yes
  11. 11.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  12. 12.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  13. 13.The two interior opposite angles of a triangle are 44° and 26°. What is the exterior angle (in degrees)?
  14. 14.In a right-angled triangle, one of the other two angles is 68°. What is the third angle (in degrees)?
  15. 15.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 51°. What is the other one (in degrees)?
  16. 16.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  18. 18.In triangle ABC, angle A = 92° and angle B = 34°. What is angle C (in degrees)?
  19. 19.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)?
  20. 20.In triangle ABC, angle A = 81° and angle B = 68°. What is angle C (in degrees)?
  21. 21.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  22. 22.The two interior opposite angles of a triangle are 78° and 47°. What is the exterior angle (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  24. 24.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  26. 26.In triangle ABC, angle A = 55° and angle B = 33°. What is angle C (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  28. 28.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)?
  29. 29.Can a triangle have sides of 10 cm, 9 cm and 22 cm? (a) Yes (b) No
  30. 30.Can a triangle have sides of 6 cm, 18 cm and 7 cm? (a) Yes (b) No
  31. 31.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  32. 32.The two interior opposite angles of a triangle are 72° and 39°. What is the exterior angle (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 100°. What is each of the other two angles (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  35. 35.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 88°. What is each of the other two angles (in degrees)?
  37. 37.Can a triangle have sides of 3 cm, 8 cm and 7 cm? (a) No (b) Yes
  38. 38.In triangle ABC, angle A = 21° and angle B = 128°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  40. 40.The longest side of a right-angled triangle is 10 cm and one of the other sides is 8 cm. How long is the third side (in cm)?

Answer key

  1. 118
  2. 90
  3. 12
  4. No
  5. 5
  6. 72
  7. 76
  8. 32
  9. 36
  10. No
  11. 25
  12. 80
  13. 70
  14. 22
  15. 55
  16. 61
  17. 58
  18. 54
  19. 15
  20. 31
  21. 24
  22. 125
  23. 17
  24. 25
  25. 11
  26. 92
  27. 30
  28. 24
  29. No
  30. No
  31. 47
  32. 111
  33. 40
  34. 13
  35. 64
  36. 46
  37. Yes
  38. 31
  39. 136
  40. 6

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