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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 937 · 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 69°. What is the third angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  4. 4.In triangle ABC, angle A = 49° and angle B = 98°. What is angle C (in degrees)?
  5. 5.In triangle ABC, angle A = 54° and angle B = 49°. What is angle C (in degrees)?
  6. 6.In triangle ABC, angle A = 81° and angle B = 21°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  9. 9.Can a triangle have sides of 11 cm, 23 cm and 10 cm? (a) No (b) Yes
  10. 10.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  11. 11.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  12. 12.Can a triangle have sides of 4 cm, 7 cm and 16 cm? (a) No (b) Yes
  13. 13.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  14. 14.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 22° each. What is the third angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  17. 17.In triangle ABC, angle A = 25° and angle B = 47°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 9 cm, 4 cm and 12 cm? (a) Yes (b) No
  19. 19.An exterior angle of a triangle is 78°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  20. 20.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)?
  21. 21.An exterior angle of a triangle is 151°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  22. 22.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  23. 23.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  24. 24.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  25. 25.In triangle ABC, angle A = 58° and angle B = 57°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  27. 27.Can a triangle have sides of 9 cm, 4 cm and 9 cm? (a) Yes (b) No
  28. 28.The longest side of a right-angled triangle is 26 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  29. 29.In triangle ABC, angle A = 73° and angle B = 31°. What is angle C (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  31. 31.Can a triangle have sides of 18 cm, 12 cm and 4 cm? (a) No (b) Yes
  32. 32.An exterior angle of a triangle is 93°. One of its two interior opposite angles is 29°. What is the other one (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  34. 34.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)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  36. 36.Can a triangle have sides of 12 cm, 7 cm and 9 cm? (a) No (b) Yes
  37. 37.The two interior opposite angles of a triangle are 23° and 34°. What is the exterior angle (in degrees)?
  38. 38.In triangle ABC, angle A = 100° and angle B = 22°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 67° each. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 8 cm, 17 cm and 7 cm? (a) No (b) Yes

Answer key

  1. 21
  2. 61
  3. 22
  4. 33
  5. 77
  6. 78
  7. 62
  8. 90
  9. No
  10. 71
  11. 45
  12. No
  13. 17
  14. 59
  15. 136
  16. 84
  17. 108
  18. Yes
  19. 53
  20. 7
  21. 72
  22. 51
  23. 38
  24. 17
  25. 65
  26. 36
  27. Yes
  28. 10
  29. 76
  30. 120
  31. No
  32. 64
  33. 70
  34. 3
  35. 60
  36. Yes
  37. 57
  38. 58
  39. 46
  40. No

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