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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 969 · 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 13°. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  3. 3.In triangle ABC, angle A = 73° and angle B = 24°. What is angle C (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  5. 5.The two interior opposite angles of a triangle are 68° and 33°. What is the exterior angle (in degrees)?
  6. 6.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  7. 7.In triangle ABC, angle A = 37° and angle B = 52°. What is angle C (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 32°. What is each of the other two angles (in degrees)?
  13. 13.Can a triangle have sides of 12 cm, 21 cm and 8 cm? (a) No (b) Yes
  14. 14.An exterior angle of a triangle is 95°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  15. 15.Can a triangle have sides of 11 cm, 10 cm and 9 cm? (a) Yes (b) No
  16. 16.The two interior opposite angles of a triangle are 79° and 56°. What is the exterior angle (in degrees)?
  17. 17.In triangle ABC, angle A = 39° and angle B = 88°. What is angle C (in degrees)?
  18. 18.In triangle ABC, angle A = 82° and angle B = 27°. What is angle C (in degrees)?
  19. 19.Can a triangle have sides of 10 cm, 21 cm and 6 cm? (a) No (b) Yes
  20. 20.Can a triangle have sides of 6 cm, 6 cm and 6 cm? (a) Yes (b) No
  21. 21.Can a triangle have sides of 5 cm, 7 cm and 3 cm? (a) No (b) Yes
  22. 22.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  23. 23.Can a triangle have sides of 4 cm, 4 cm and 1 cm? (a) No (b) Yes
  24. 24.Can a triangle have sides of 3 cm, 10 cm and 9 cm? (a) Yes (b) No
  25. 25.An exterior angle of a triangle is 52°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  26. 26.In triangle ABC, angle A = 81° and angle B = 46°. What is angle C (in degrees)?
  27. 27.In triangle ABC, angle A = 45° and angle B = 79°. What is angle C (in degrees)?
  28. 28.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  29. 29.Can a triangle have sides of 7 cm, 3 cm and 9 cm? (a) Yes (b) No
  30. 30.In triangle ABC, angle A = 39° and angle B = 95°. What is angle C (in degrees)?
  31. 31.Can a triangle have sides of 9 cm, 17 cm and 5 cm? (a) Yes (b) No
  32. 32.The two interior opposite angles of a triangle are 44° and 72°. What is the exterior angle (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 44° and 23°. What is the exterior angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  36. 36.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  37. 37.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 60°. What is the other one (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 54°. What is the third angle (in degrees)?
  39. 39.Can a triangle have sides of 12 cm, 6 cm and 21 cm? (a) Yes (b) No
  40. 40.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?

Answer key

  1. 77
  2. 27
  3. 83
  4. 20
  5. 101
  6. 41
  7. 91
  8. 29
  9. 52
  10. 31
  11. 72
  12. 74
  13. No
  14. 20
  15. Yes
  16. 135
  17. 53
  18. 71
  19. No
  20. Yes
  21. Yes
  22. 120
  23. Yes
  24. Yes
  25. 20
  26. 53
  27. 56
  28. 54
  29. Yes
  30. 46
  31. No
  32. 116
  33. 64
  34. 67
  35. 61
  36. 45
  37. 31
  38. 36
  39. No
  40. 17

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