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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 520 · 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 = 78° and angle B = 34°. What is angle C (in degrees)?
  2. 2.The longest side of a right-angled triangle is 30 cm and one of the other sides is 18 cm. How long is the third side (in cm)?
  3. 3.The two interior opposite angles of a triangle are 59° and 64°. What is the exterior angle (in degrees)?
  4. 4.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)?
  5. 5.In triangle ABC, angle A = 26° and angle B = 33°. What is angle C (in degrees)?
  6. 6.The longest side of a right-angled triangle is 5 cm and one of the other sides is 4 cm. How long is the third side (in cm)?
  7. 7.In a right-angled triangle, one of the other two angles is 78°. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 79° and angle B = 24°. What is angle C (in degrees)?
  9. 9.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  10. 10.Can a triangle have sides of 4 cm, 12 cm and 11 cm? (a) Yes (b) No
  11. 11.In triangle ABC, angle A = 39° and angle B = 52°. What is angle C (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  13. 13.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)?
  14. 14.The two interior opposite angles of a triangle are 78° and 21°. What is the exterior angle (in degrees)?
  15. 15.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  16. 16.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)?
  17. 17.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  18. 18.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)?
  19. 19.In triangle ABC, angle A = 26° and angle B = 95°. What is angle C (in degrees)?
  20. 20.In triangle ABC, angle A = 43° and angle B = 96°. What is angle C (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 30° and angle B = 124°. What is angle C (in degrees)?
  24. 24.An exterior angle of a triangle is 124°. One of its two interior opposite angles is 50°. What is the other one (in degrees)?
  25. 25.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  26. 26.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  27. 27.The longest side of a right-angled triangle is 15 cm and one of the other sides is 9 cm. How long is the third side (in cm)?
  28. 28.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  29. 29.In triangle ABC, angle A = 57° and angle B = 69°. What is angle C (in degrees)?
  30. 30.An exterior angle of a triangle is 70°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  31. 31.The longest side of a right-angled triangle is 39 cm and one of the other sides is 36 cm. How long is the third side (in cm)?
  32. 32.The two interior opposite angles of a triangle are 36° and 78°. What is the exterior angle (in degrees)?
  33. 33.In an isosceles triangle, the two equal angles are 45° each. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 72°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 54° and angle B = 31°. What is angle C (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 70°. What is the third angle (in degrees)?
  37. 37.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)?
  38. 38.Can a triangle have sides of 8 cm, 4 cm and 4 cm? (a) Yes (b) No
  39. 39.In a right-angled triangle, one of the other two angles is 32°. What is the third 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. 68
  2. 24
  3. 123
  4. 12
  5. 121
  6. 3
  7. 12
  8. 77
  9. 13
  10. Yes
  11. 89
  12. 56
  13. 8
  14. 99
  15. 20
  16. 24
  17. 38
  18. 15
  19. 59
  20. 41
  21. 90
  22. 71
  23. 26
  24. 74
  25. 25
  26. 20
  27. 12
  28. 72
  29. 54
  30. 27
  31. 15
  32. 114
  33. 90
  34. 18
  35. 95
  36. 20
  37. 24
  38. No
  39. 58
  40. 55

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