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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 839 · 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.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)?
  2. 2.An exterior angle of a triangle is 51°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  3. 3.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 14°. What is the third angle (in degrees)?
  5. 5.An exterior angle of a triangle is 92°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 28°. What is each of the other two angles (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  8. 8.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  9. 9.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 37°. What is the other one (in degrees)?
  10. 10.In triangle ABC, angle A = 57° and angle B = 69°. What is angle C (in degrees)?
  11. 11.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  12. 12.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)?
  13. 13.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  14. 14.Can a triangle have sides of 5 cm, 3 cm and 3 cm? (a) Yes (b) No
  15. 15.The two interior opposite angles of a triangle are 69° and 27°. What is the exterior angle (in degrees)?
  16. 16.Can a triangle have sides of 14 cm, 4 cm and 8 cm? (a) Yes (b) No
  17. 17.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  18. 18.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 42° and angle B = 72°. What is angle C (in degrees)?
  20. 20.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  21. 21.In triangle ABC, angle A = 34° and angle B = 28°. What is angle C (in degrees)?
  22. 22.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)?
  23. 23.In triangle ABC, angle A = 100° and angle B = 35°. What is angle C (in degrees)?
  24. 24.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)?
  25. 25.Can a triangle have sides of 10 cm, 9 cm and 2 cm? (a) No (b) Yes
  26. 26.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  28. 28.In triangle ABC, angle A = 66° and angle B = 86°. What is angle C (in degrees)?
  29. 29.An exterior angle of a triangle is 60°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  31. 31.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 2 cm, 3 cm and 2 cm? (a) No (b) Yes
  33. 33.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 122°. What is each of the other two angles (in degrees)?
  36. 36.Can a triangle have sides of 3 cm, 4 cm and 2 cm? (a) Yes (b) No
  37. 37.In an isosceles triangle, the angle between the two equal sides is 70°. What is each of the other two angles (in degrees)?
  38. 38.Can a triangle have sides of 18 cm, 8 cm and 5 cm? (a) No (b) Yes
  39. 39.Can a triangle have sides of 7 cm, 12 cm and 6 cm? (a) No (b) Yes
  40. 40.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?

Answer key

  1. 24
  2. 29
  3. 50
  4. 76
  5. 69
  6. 76
  7. 79
  8. 55
  9. 71
  10. 54
  11. 36
  12. 7
  13. 48
  14. Yes
  15. 96
  16. No
  17. 25
  18. 47
  19. 66
  20. 27
  21. 118
  22. 15
  23. 45
  24. 8
  25. Yes
  26. 36
  27. 71
  28. 28
  29. 20
  30. 16
  31. 66
  32. Yes
  33. 10
  34. 5
  35. 29
  36. Yes
  37. 55
  38. No
  39. Yes
  40. 90

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