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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 577 · 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 27°. What is the third angle (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  3. 3.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  4. 4.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)?
  5. 5.Can a triangle have sides of 2 cm, 4 cm and 3 cm? (a) No (b) Yes
  6. 6.In triangle ABC, angle A = 81° and angle B = 63°. What is angle C (in degrees)?
  7. 7.In triangle ABC, angle A = 47° and angle B = 24°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 65° and angle B = 87°. What is angle C (in degrees)?
  9. 9.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  10. 10.In an isosceles triangle, the two equal angles are 69° each. What is the third angle (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  12. 12.An exterior angle of a triangle is 94°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  13. 13.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)?
  14. 14.Can a triangle have sides of 8 cm, 11 cm and 5 cm? (a) Yes (b) No
  15. 15.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  16. 16.Can a triangle have sides of 11 cm, 17 cm and 3 cm? (a) Yes (b) No
  17. 17.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (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 an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  20. 20.Can a triangle have sides of 3 cm, 12 cm and 10 cm? (a) Yes (b) No
  21. 21.Can a triangle have sides of 12 cm, 12 cm and 3 cm? (a) Yes (b) No
  22. 22.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  23. 23.In triangle ABC, angle A = 69° and angle B = 40°. What is angle C (in degrees)?
  24. 24.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 29°. What is the third angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  27. 27.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 61°. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 13 cm, 5 cm and 10 cm? (a) Yes (b) No
  30. 30.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  31. 31.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  32. 32.In triangle ABC, angle A = 41° and angle B = 72°. What is angle C (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 25° and 67°. What is the exterior angle (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 54° and 22°. What is the exterior angle (in degrees)?
  36. 36.Can a triangle have sides of 2 cm, 2 cm and 1 cm? (a) Yes (b) No
  37. 37.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  38. 38.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  39. 39.In triangle ABC, angle A = 72° and angle B = 83°. What is angle C (in degrees)?
  40. 40.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?

Answer key

  1. 63
  2. 17
  3. 12
  4. 24
  5. Yes
  6. 36
  7. 109
  8. 28
  9. 84
  10. 42
  11. 140
  12. 62
  13. 7
  14. Yes
  15. 31
  16. No
  17. 77
  18. 15
  19. 56
  20. Yes
  21. Yes
  22. 31
  23. 71
  24. 14
  25. 61
  26. 45
  27. 106
  28. 29
  29. Yes
  30. 20
  31. 15
  32. 67
  33. 92
  34. 94
  35. 76
  36. Yes
  37. 90
  38. 20
  39. 25
  40. 14

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