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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 738 · 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 5 cm, 3 cm and 5 cm? (a) No (b) Yes
  2. 2.In triangle ABC, angle A = 23° and angle B = 129°. What is angle C (in degrees)?
  3. 3.In triangle ABC, angle A = 61° and angle B = 43°. What is angle C (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  5. 5.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  6. 6.Can a triangle have sides of 12 cm, 17 cm and 3 cm? (a) Yes (b) No
  7. 7.The two interior opposite angles of a triangle are 73° and 20°. What is the exterior angle (in degrees)?
  8. 8.In triangle ABC, angle A = 73° and angle B = 28°. What is angle C (in degrees)?
  9. 9.Can a triangle have sides of 10 cm, 7 cm and 17 cm? (a) Yes (b) No
  10. 10.Can a triangle have sides of 2 cm, 5 cm and 2 cm? (a) Yes (b) No
  11. 11.In triangle ABC, angle A = 48° and angle B = 34°. What is angle C (in degrees)?
  12. 12.Can a triangle have sides of 7 cm, 9 cm and 21 cm? (a) No (b) Yes
  13. 13.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)?
  14. 14.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  15. 15.Can a triangle have sides of 4 cm, 5 cm and 2 cm? (a) Yes (b) No
  16. 16.In triangle ABC, angle A = 51° and angle B = 34°. What is angle C (in degrees)?
  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 triangle ABC, angle A = 65° and angle B = 89°. What is angle C (in degrees)?
  19. 19.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  21. 21.Can a triangle have sides of 5 cm, 9 cm and 18 cm? (a) No (b) Yes
  22. 22.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 30° and 23°. What is the exterior angle (in degrees)?
  24. 24.In triangle ABC, angle A = 47° and angle B = 47°. What is angle C (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  27. 27.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  28. 28.In triangle ABC, angle A = 28° and angle B = 47°. What is angle C (in degrees)?
  29. 29.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 71°. What is the third angle (in degrees)?
  31. 31.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  32. 32.In a right-angled triangle, one of the other two angles is 57°. What is the third angle (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 21° and 63°. What is the exterior angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  35. 35.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)?
  36. 36.Can a triangle have sides of 9 cm, 12 cm and 26 cm? (a) Yes (b) No
  37. 37.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  38. 38.Can a triangle have sides of 9 cm, 8 cm and 19 cm? (a) Yes (b) No
  39. 39.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  40. 40.An exterior angle of a triangle is 87°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?

Answer key

  1. Yes
  2. 28
  3. 76
  4. 63
  5. 80
  6. No
  7. 93
  8. 79
  9. No
  10. No
  11. 98
  12. No
  13. 8
  14. 45
  15. Yes
  16. 95
  17. 25
  18. 26
  19. 20
  20. 64
  21. No
  22. 60
  23. 53
  24. 86
  25. 36
  26. 17
  27. 52
  28. 105
  29. 38
  30. 19
  31. 100
  32. 33
  33. 84
  34. 51
  35. 12
  36. No
  37. 25
  38. No
  39. 14
  40. 22

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