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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 269 · 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.In an isosceles triangle, the two equal angles are 66° each. What is the third angle (in degrees)?
  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.Can a triangle have sides of 16 cm, 2 cm and 12 cm? (a) No (b) Yes
  4. 4.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  6. 6.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 80° and angle B = 35°. What is angle C (in degrees)?
  10. 10.Can a triangle have sides of 11 cm, 20 cm and 6 cm? (a) Yes (b) No
  11. 11.Can a triangle have sides of 7 cm, 8 cm and 15 cm? (a) No (b) Yes
  12. 12.The two interior opposite angles of a triangle are 49° and 30°. What is the exterior angle (in degrees)?
  13. 13.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  14. 14.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  15. 15.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  16. 16.The two shorter sides of a right-angled triangle are 5 cm and 12 cm. How long is the longest side (in cm)?
  17. 17.In an isosceles triangle, the angle between the two equal sides is 56°. What is each of the other two angles (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  19. 19.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  20. 20.Can a triangle have sides of 11 cm, 12 cm and 4 cm? (a) Yes (b) No
  21. 21.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  22. 22.Can a triangle have sides of 12 cm, 26 cm and 10 cm? (a) Yes (b) No
  23. 23.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)?
  24. 24.The two interior opposite angles of a triangle are 65° and 27°. What is the exterior angle (in degrees)?
  25. 25.Can a triangle have sides of 7 cm, 7 cm and 1 cm? (a) No (b) Yes
  26. 26.In a right-angled triangle, one of the other two angles is 79°. What is the third angle (in degrees)?
  27. 27.Can a triangle have sides of 8 cm, 6 cm and 19 cm? (a) No (b) Yes
  28. 28.In triangle ABC, angle A = 72° and angle B = 66°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 36°. What is each of the other two angles (in degrees)?
  30. 30.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  31. 31.Can a triangle have sides of 14 cm, 6 cm and 5 cm? (a) Yes (b) No
  32. 32.In triangle ABC, angle A = 71° and angle B = 42°. What is angle C (in degrees)?
  33. 33.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 26°. What is the other one (in degrees)?
  34. 34.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  35. 35.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)?
  36. 36.In triangle ABC, angle A = 28° and angle B = 75°. What is angle C (in degrees)?
  37. 37.Can a triangle have sides of 6 cm, 7 cm and 15 cm? (a) Yes (b) No
  38. 38.In triangle ABC, angle A = 57° and angle B = 45°. What is angle C (in degrees)?
  39. 39.In an isosceles triangle, the two equal angles are 43° each. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 9 cm, 9 cm and 18 cm? (a) Yes (b) No

Answer key

  1. 48
  2. 24
  3. No
  4. 50
  5. 30
  6. 10
  7. 52
  8. 77
  9. 65
  10. No
  11. No
  12. 79
  13. 56
  14. 20
  15. 54
  16. 13
  17. 62
  18. 80
  19. 20
  20. Yes
  21. 25
  22. No
  23. 8
  24. 92
  25. Yes
  26. 11
  27. No
  28. 42
  29. 72
  30. 50
  31. No
  32. 67
  33. 53
  34. 17
  35. 4
  36. 77
  37. No
  38. 78
  39. 94
  40. No

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