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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 568 · 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 angle between the two equal sides is 52°. What is each of the other two angles (in degrees)?
  2. 2.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  3. 3.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  4. 4.In triangle ABC, angle A = 65° and angle B = 49°. What is angle C (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 80°. What is each of the other two angles (in degrees)?
  6. 6.An exterior angle of a triangle is 113°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  7. 7.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)?
  8. 8.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  9. 9.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  10. 10.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  11. 11.Can a triangle have sides of 10 cm, 6 cm and 18 cm? (a) No (b) Yes
  12. 12.In triangle ABC, angle A = 21° and angle B = 79°. What is angle C (in degrees)?
  13. 13.The two shorter sides of a right-angled triangle are 6 cm and 8 cm. How long is the longest side (in cm)?
  14. 14.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  15. 15.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)?
  16. 16.In triangle ABC, angle A = 90° and angle B = 23°. What is angle C (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 32° and 49°. What is the exterior angle (in degrees)?
  18. 18.An exterior angle of a triangle is 146°. One of its two interior opposite angles is 68°. What is the other one (in degrees)?
  19. 19.Can a triangle have sides of 7 cm, 16 cm and 11 cm? (a) No (b) Yes
  20. 20.The angles of a triangle are in the ratio 3 : 3 : 4. What is the smallest angle (in degrees)?
  21. 21.In triangle ABC, angle A = 77° and angle B = 38°. What is angle C (in degrees)?
  22. 22.In triangle ABC, angle A = 30° and angle B = 125°. What is angle C (in degrees)?
  23. 23.Can a triangle have sides of 5 cm, 2 cm and 10 cm? (a) No (b) Yes
  24. 24.An exterior angle of a triangle is 121°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  25. 25.An exterior angle of a triangle is 114°. One of its two interior opposite angles is 80°. What is the other one (in degrees)?
  26. 26.Can a triangle have sides of 3 cm, 3 cm and 9 cm? (a) No (b) Yes
  27. 27.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  28. 28.In triangle ABC, angle A = 31° and angle B = 48°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 83° and angle B = 22°. What is angle C (in degrees)?
  30. 30.Can a triangle have sides of 24 cm, 12 cm and 10 cm? (a) Yes (b) No
  31. 31.In a right-angled triangle, one of the other two angles is 21°. What is the third angle (in degrees)?
  32. 32.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)?
  33. 33.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  34. 34.In triangle ABC, angle A = 26° and angle B = 60°. What is angle C (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  36. 36.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)?
  37. 37.An exterior angle of a triangle is 96°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  38. 38.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  39. 39.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  40. 40.Can a triangle have sides of 9 cm, 3 cm and 3 cm? (a) No (b) Yes

Answer key

  1. 64
  2. 70
  3. 56
  4. 66
  5. 50
  6. 66
  7. 8
  8. 25
  9. 17
  10. 20
  11. No
  12. 80
  13. 10
  14. 77
  15. 5
  16. 67
  17. 81
  18. 78
  19. Yes
  20. 54
  21. 65
  22. 25
  23. No
  24. 48
  25. 34
  26. No
  27. 18
  28. 101
  29. 75
  30. No
  31. 69
  32. 24
  33. 90
  34. 94
  35. 25
  36. 12
  37. 33
  38. 40
  39. 52
  40. No

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