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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 764 · 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.An exterior angle of a triangle is 41°. One of its two interior opposite angles is 20°. What is the other one (in degrees)?
  2. 2.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  3. 3.An exterior angle of a triangle is 67°. One of its two interior opposite angles is 38°. What is the other one (in degrees)?
  4. 4.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)?
  5. 5.Can a triangle have sides of 5 cm, 14 cm and 8 cm? (a) No (b) Yes
  6. 6.Can a triangle have sides of 2 cm, 2 cm and 1 cm? (a) No (b) Yes
  7. 7.An exterior angle of a triangle is 115°. One of its two interior opposite angles is 76°. What is the other one (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  9. 9.In triangle ABC, angle A = 82° and angle B = 22°. What is angle C (in degrees)?
  10. 10.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  11. 11.In triangle ABC, angle A = 100° and angle B = 23°. What is angle C (in degrees)?
  12. 12.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  13. 13.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  14. 14.Can a triangle have sides of 5 cm, 13 cm and 8 cm? (a) Yes (b) No
  15. 15.In triangle ABC, angle A = 52° and angle B = 32°. What is angle C (in degrees)?
  16. 16.In triangle ABC, angle A = 63° and angle B = 54°. What is angle C (in degrees)?
  17. 17.The two interior opposite angles of a triangle are 29° and 20°. What is the exterior angle (in degrees)?
  18. 18.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  19. 19.Can a triangle have sides of 6 cm, 12 cm and 19 cm? (a) No (b) Yes
  20. 20.In triangle ABC, angle A = 64° and angle B = 73°. What is angle C (in degrees)?
  21. 21.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  22. 22.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  23. 23.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  24. 24.In triangle ABC, angle A = 24° and angle B = 53°. What is angle C (in degrees)?
  25. 25.The two interior opposite angles of a triangle are 57° and 52°. What is the exterior angle (in degrees)?
  26. 26.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 25°. What is the third angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 106°. What is each of the other two angles (in degrees)?
  30. 30.The two interior opposite angles of a triangle are 73° and 31°. What is the exterior angle (in degrees)?
  31. 31.Can a triangle have sides of 14 cm, 2 cm and 7 cm? (a) Yes (b) No
  32. 32.Can a triangle have sides of 9 cm, 7 cm and 8 cm? (a) Yes (b) No
  33. 33.The longest side of a right-angled triangle is 17 cm and one of the other sides is 8 cm. How long is the third side (in cm)?
  34. 34.An exterior angle of a triangle is 118°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 31° and 32°. What is the exterior angle (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  37. 37.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  38. 38.The two interior opposite angles of a triangle are 57° and 54°. What is the exterior angle (in degrees)?
  39. 39.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  40. 40.In triangle ABC, angle A = 67° and angle B = 49°. What is angle C (in degrees)?

Answer key

  1. 21
  2. 26
  3. 29
  4. 7
  5. No
  6. Yes
  7. 39
  8. 52
  9. 76
  10. 100
  11. 57
  12. 18
  13. 23
  14. No
  15. 96
  16. 63
  17. 49
  18. 36
  19. No
  20. 43
  21. 16
  22. 90
  23. 36
  24. 103
  25. 109
  26. 20
  27. 65
  28. 72
  29. 37
  30. 104
  31. No
  32. Yes
  33. 15
  34. 55
  35. 63
  36. 60
  37. 80
  38. 111
  39. 90
  40. 64

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