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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 863 · 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.Can a triangle have sides of 8 cm, 6 cm and 11 cm? (a) Yes (b) No
  2. 2.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  3. 3.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 26° and angle B = 28°. What is angle C (in degrees)?
  5. 5.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)?
  6. 6.In an isosceles triangle, the two equal angles are 20° each. What is the third angle (in degrees)?
  7. 7.In triangle ABC, angle A = 37° and angle B = 79°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 39° and angle B = 85°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 28°. What is the third angle (in degrees)?
  10. 10.An exterior angle of a triangle is 91°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  11. 11.Can a triangle have sides of 6 cm, 4 cm and 7 cm? (a) No (b) Yes
  12. 12.Can a triangle have sides of 3 cm, 7 cm and 3 cm? (a) Yes (b) No
  13. 13.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  14. 14.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 2 : 2. What is the biggest angle (in degrees)?
  16. 16.In triangle ABC, angle A = 22° and angle B = 57°. What is angle C (in degrees)?
  17. 17.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  18. 18.In an isosceles triangle, the angle between the two equal sides is 148°. What is each of the other two angles (in degrees)?
  19. 19.An exterior angle of a triangle is 76°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  20. 20.In triangle ABC, angle A = 61° and angle B = 39°. What is angle C (in degrees)?
  21. 21.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 77°. What is the other one (in degrees)?
  22. 22.In triangle ABC, angle A = 52° and angle B = 102°. What is angle C (in degrees)?
  23. 23.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  24. 24.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 51° and 32°. What is the exterior angle (in degrees)?
  26. 26.In triangle ABC, angle A = 38° and angle B = 118°. What is angle C (in degrees)?
  27. 27.Can a triangle have sides of 6 cm, 11 cm and 20 cm? (a) Yes (b) No
  28. 28.In triangle ABC, angle A = 56° and angle B = 64°. What is angle C (in degrees)?
  29. 29.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  31. 31.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  32. 32.Can a triangle have sides of 6 cm, 6 cm and 17 cm? (a) Yes (b) No
  33. 33.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  34. 34.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  35. 35.In triangle ABC, angle A = 70° and angle B = 36°. What is angle C (in degrees)?
  36. 36.Can a triangle have sides of 10 cm, 9 cm and 6 cm? (a) Yes (b) No
  37. 37.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  38. 38.An exterior angle of a triangle is 72°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  39. 39.Can a triangle have sides of 9 cm, 19 cm and 9 cm? (a) Yes (b) No
  40. 40.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?

Answer key

  1. Yes
  2. 8
  3. 45
  4. 126
  5. 7
  6. 140
  7. 64
  8. 56
  9. 62
  10. 36
  11. Yes
  12. No
  13. 120
  14. 59
  15. 72
  16. 101
  17. 28
  18. 16
  19. 35
  20. 80
  21. 27
  22. 26
  23. 25
  24. 80
  25. 83
  26. 24
  27. No
  28. 60
  29. 40
  30. 20
  31. 72
  32. No
  33. 15
  34. 4
  35. 74
  36. Yes
  37. 39
  38. 51
  39. No
  40. 51

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