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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 691 · 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 6 cm, 11 cm and 22 cm? (a) No (b) Yes
  2. 2.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)?
  3. 3.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  4. 4.In triangle ABC, angle A = 66° and angle B = 47°. What is angle C (in degrees)?
  5. 5.Can a triangle have sides of 7 cm, 5 cm and 9 cm? (a) No (b) Yes
  6. 6.In triangle ABC, angle A = 70° and angle B = 63°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 65°. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  9. 9.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 40° and 44°. What is the exterior angle (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  12. 12.In an isosceles triangle, the two equal angles are 53° each. What is the third angle (in degrees)?
  13. 13.Can a triangle have sides of 6 cm, 8 cm and 6 cm? (a) Yes (b) No
  14. 14.Can a triangle have sides of 2 cm, 6 cm and 6 cm? (a) Yes (b) No
  15. 15.The two interior opposite angles of a triangle are 80° and 28°. What is the exterior angle (in degrees)?
  16. 16.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  17. 17.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  18. 18.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  19. 19.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  20. 20.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  22. 22.In triangle ABC, angle A = 95° and angle B = 41°. What is angle C (in degrees)?
  23. 23.Can a triangle have sides of 1 cm, 8 cm and 8 cm? (a) No (b) Yes
  24. 24.The two interior opposite angles of a triangle are 22° and 69°. What is the exterior angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  26. 26.The two interior opposite angles of a triangle are 56° and 39°. What is the exterior angle (in degrees)?
  27. 27.In triangle ABC, angle A = 56° and angle B = 68°. What is angle C (in degrees)?
  28. 28.In an isosceles triangle, the angle between the two equal sides is 120°. What is each of the other two angles (in degrees)?
  29. 29.In triangle ABC, angle A = 20° and angle B = 24°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 25° and angle B = 53°. What is angle C (in degrees)?
  31. 31.Can a triangle have sides of 13 cm, 7 cm and 2 cm? (a) Yes (b) No
  32. 32.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  33. 33.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)?
  34. 34.In an isosceles triangle, the two equal angles are 80° each. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  36. 36.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  37. 37.Can a triangle have sides of 10 cm, 24 cm and 10 cm? (a) Yes (b) No
  38. 38.In triangle ABC, angle A = 30° and angle B = 22°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 18 cm, 12 cm and 2 cm? (a) Yes (b) No

Answer key

  1. No
  2. 24
  3. 26
  4. 67
  5. Yes
  6. 47
  7. 25
  8. 37
  9. 84
  10. 84
  11. 80
  12. 74
  13. Yes
  14. Yes
  15. 108
  16. 36
  17. 16
  18. 31
  19. 12
  20. 20
  21. 90
  22. 44
  23. Yes
  24. 91
  25. 138
  26. 95
  27. 56
  28. 30
  29. 136
  30. 102
  31. No
  32. 80
  33. 8
  34. 20
  35. 60
  36. 116
  37. No
  38. 128
  39. 64
  40. No

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