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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 775 · 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 two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  2. 2.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 58°. What is the other one (in degrees)?
  3. 3.In triangle ABC, angle A = 71° and angle B = 47°. What is angle C (in degrees)?
  4. 4.An exterior angle of a triangle is 103°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  5. 5.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  6. 6.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?
  7. 7.Can a triangle have sides of 11 cm, 7 cm and 2 cm? (a) No (b) Yes
  8. 8.An exterior angle of a triangle is 130°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  9. 9.Can a triangle have sides of 2 cm, 3 cm and 4 cm? (a) No (b) Yes
  10. 10.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  11. 11.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  13. 13.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  14. 14.In triangle ABC, angle A = 32° and angle B = 35°. What is angle C (in degrees)?
  15. 15.In triangle ABC, angle A = 61° and angle B = 32°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 54° and angle B = 53°. What is angle C (in degrees)?
  17. 17.In triangle ABC, angle A = 79° and angle B = 80°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 24° and 62°. What is the exterior angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  20. 20.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 32° and 28°. What is the exterior angle (in degrees)?
  22. 22.An exterior angle of a triangle is 58°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  23. 23.An exterior angle of a triangle is 139°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  24. 24.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)?
  25. 25.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)?
  26. 26.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  27. 27.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  30. 30.In triangle ABC, angle A = 59° and angle B = 77°. What is angle C (in degrees)?
  31. 31.Can a triangle have sides of 7 cm, 1 cm and 7 cm? (a) Yes (b) No
  32. 32.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  34. 34.Can a triangle have sides of 4 cm, 6 cm and 2 cm? (a) No (b) Yes
  35. 35.The two interior opposite angles of a triangle are 68° and 74°. What is the exterior angle (in degrees)?
  36. 36.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)?
  37. 37.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  38. 38.In an isosceles triangle, the two equal angles are 29° each. What is the third angle (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  40. 40.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?

Answer key

  1. 25
  2. 32
  3. 62
  4. 70
  5. 36
  6. 40
  7. No
  8. 56
  9. Yes
  10. 25
  11. 20
  12. 65
  13. 100
  14. 113
  15. 87
  16. 73
  17. 21
  18. 86
  19. 43
  20. 90
  21. 60
  22. 37
  23. 66
  24. 10
  25. 15
  26. 75
  27. 66
  28. 10
  29. 66
  30. 44
  31. Yes
  32. 90
  33. 19
  34. No
  35. 142
  36. 15
  37. 48
  38. 122
  39. 5
  40. 12

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