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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 305 · 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, 7 cm and 10 cm? (a) Yes (b) No
  2. 2.Can a triangle have sides of 4 cm, 8 cm and 4 cm? (a) Yes (b) No
  3. 3.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  5. 5.Can a triangle have sides of 10 cm, 9 cm and 16 cm? (a) No (b) Yes
  6. 6.In an isosceles triangle, the angle between the two equal sides is 110°. What is each of the other two angles (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 60°. What is the third angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  9. 9.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 54°. What is the other one (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 4 cm and 3 cm. How long is the longest side (in cm)?
  11. 11.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)?
  12. 12.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  14. 14.An exterior angle of a triangle is 89°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  15. 15.Can a triangle have sides of 6 cm, 5 cm and 11 cm? (a) Yes (b) No
  16. 16.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 7 : 9. What is the biggest angle (in degrees)?
  19. 19.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  20. 20.The two interior opposite angles of a triangle are 67° and 24°. What is the exterior angle (in degrees)?
  21. 21.In triangle ABC, angle A = 39° and angle B = 83°. What is angle C (in degrees)?
  22. 22.Can a triangle have sides of 10 cm, 6 cm and 6 cm? (a) No (b) Yes
  23. 23.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  25. 25.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?
  26. 26.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  27. 27.An exterior angle of a triangle is 90°. One of its two interior opposite angles is 41°. What is the other one (in degrees)?
  28. 28.Can a triangle have sides of 11 cm, 15 cm and 2 cm? (a) Yes (b) No
  29. 29.An exterior angle of a triangle is 79°. One of its two interior opposite angles is 22°. What is the other one (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 32°. What is the third angle (in degrees)?
  31. 31.Can a triangle have sides of 6 cm, 2 cm and 2 cm? (a) No (b) Yes
  32. 32.In triangle ABC, angle A = 80° and angle B = 43°. What is angle C (in degrees)?
  33. 33.In a right-angled triangle, one of the other two angles is 53°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 23°. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the angle between the two equal sides is 108°. What is each of the other two angles (in degrees)?
  36. 36.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)?
  37. 37.In an isosceles triangle, the angle between the two equal sides is 66°. What is each of the other two angles (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 46° and 35°. What is the exterior angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 32° and 68°. What is the exterior angle (in degrees)?

Answer key

  1. Yes
  2. No
  3. 18
  4. 50
  5. Yes
  6. 35
  7. 30
  8. 90
  9. 68
  10. 5
  11. 7
  12. 54
  13. 17
  14. 68
  15. No
  16. 74
  17. 84
  18. 90
  19. 5
  20. 91
  21. 58
  22. Yes
  23. 100
  24. 36
  25. 34
  26. 112
  27. 49
  28. No
  29. 57
  30. 58
  31. No
  32. 57
  33. 37
  34. 67
  35. 36
  36. 20
  37. 57
  38. 81
  39. 75
  40. 100

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