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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 459 · 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.

NameDateTime takenScore ___ / 40
  1. 1.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  2. 2.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 15°. What is the third angle (in degrees)?
  4. 4.The two interior opposite angles of a triangle are 80° and 38°. What is the exterior angle (in degrees)?
  5. 5.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 43°. What is the other one (in degrees)?
  6. 6.Can a triangle have sides of 11 cm, 11 cm and 2 cm? (a) No (b) Yes
  7. 7.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  8. 8.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  9. 9.An exterior angle of a triangle is 45°. One of its two interior opposite angles is 24°. What is the other one (in degrees)?
  10. 10.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  11. 11.Can a triangle have sides of 3 cm, 8 cm and 16 cm? (a) No (b) Yes
  12. 12.Can a triangle have sides of 5 cm, 15 cm and 5 cm? (a) No (b) Yes
  13. 13.In a right-angled triangle, one of the other two angles is 62°. What is the third angle (in degrees)?
  14. 14.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  15. 15.The two shorter sides of a right-angled triangle are 24 cm and 18 cm. How long is the longest side (in cm)?
  16. 16.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 79° and 27°. What is the exterior angle (in degrees)?
  18. 18.An exterior angle of a triangle is 155°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 54° and 57°. What is the exterior angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  23. 23.The longest side of a right-angled triangle is 20 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  24. 24.In triangle ABC, angle A = 25° and angle B = 125°. What is angle C (in degrees)?
  25. 25.In triangle ABC, angle A = 78° and angle B = 76°. What is angle C (in degrees)?
  26. 26.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  27. 27.An exterior angle of a triangle is 102°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  28. 28.The two interior opposite angles of a triangle are 48° and 54°. What is the exterior angle (in degrees)?
  29. 29.In triangle ABC, angle A = 40° and angle B = 27°. What is angle C (in degrees)?
  30. 30.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  31. 31.In triangle ABC, angle A = 20° and angle B = 96°. What is angle C (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  33. 33.In triangle ABC, angle A = 78° and angle B = 28°. What is angle C (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  35. 35.An exterior angle of a triangle is 109°. One of its two interior opposite angles is 72°. What is the other one (in degrees)?
  36. 36.In an isosceles triangle, the angle between the two equal sides is 158°. What is each of the other two angles (in degrees)?
  37. 37.An exterior angle of a triangle is 137°. One of its two interior opposite angles is 79°. What is the other one (in degrees)?
  38. 38.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 83° each. What is the third angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 67° and 39°. What is the exterior angle (in degrees)?

Answer key

  1. 25
  2. 78
  3. 75
  4. 118
  5. 66
  6. Yes
  7. 30
  8. 25
  9. 21
  10. 36
  11. No
  12. No
  13. 28
  14. 44
  15. 30
  16. 20
  17. 106
  18. 80
  19. 20
  20. 71
  21. 111
  22. 84
  23. 16
  24. 30
  25. 26
  26. 72
  27. 69
  28. 102
  29. 113
  30. 13
  31. 64
  32. 26
  33. 74
  34. 60
  35. 37
  36. 11
  37. 58
  38. 72
  39. 14
  40. 106

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