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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 448 · 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 49° each. What is the third angle (in degrees)?
  2. 2.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 65° and angle B = 80°. What is angle C (in degrees)?
  4. 4.The two shorter sides of a right-angled triangle are 24 cm and 10 cm. How long is the longest side (in cm)?
  5. 5.In triangle ABC, angle A = 65° and angle B = 28°. What is angle C (in degrees)?
  6. 6.Can a triangle have sides of 19 cm, 10 cm and 5 cm? (a) No (b) Yes
  7. 7.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  8. 8.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  9. 9.Can a triangle have sides of 7 cm, 6 cm and 18 cm? (a) Yes (b) No
  10. 10.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  11. 11.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  13. 13.Can a triangle have sides of 12 cm, 4 cm and 4 cm? (a) No (b) Yes
  14. 14.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  15. 15.An exterior angle of a triangle is 86°. One of its two interior opposite angles is 32°. What is the other one (in degrees)?
  16. 16.In triangle ABC, angle A = 62° and angle B = 34°. What is angle C (in degrees)?
  17. 17.Can a triangle have sides of 11 cm, 9 cm and 3 cm? (a) No (b) Yes
  18. 18.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 82° and angle B = 31°. What is angle C (in degrees)?
  20. 20.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 27° and 38°. What is the exterior angle (in degrees)?
  22. 22.Can a triangle have sides of 7 cm, 3 cm and 3 cm? (a) Yes (b) No
  23. 23.In triangle ABC, angle A = 66° and angle B = 54°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  25. 25.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  26. 26.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)?
  27. 27.In triangle ABC, angle A = 22° and angle B = 68°. What is angle C (in degrees)?
  28. 28.In triangle ABC, angle A = 81° and angle B = 59°. What is angle C (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 70° and 28°. What is the exterior angle (in degrees)?
  30. 30.In a right-angled triangle, one of the other two angles is 38°. What is the third angle (in degrees)?
  31. 31.The two interior opposite angles of a triangle are 32° and 40°. What is the exterior angle (in degrees)?
  32. 32.The two shorter sides of a right-angled triangle are 8 cm and 15 cm. How long is the longest side (in cm)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 26°. What is each of the other two angles (in degrees)?
  34. 34.In triangle ABC, angle A = 63° and angle B = 78°. What is angle C (in degrees)?
  35. 35.An exterior angle of a triangle is 121°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  36. 36.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 48°. What is the other one (in degrees)?
  37. 37.In triangle ABC, angle A = 64° and angle B = 43°. What is angle C (in degrees)?
  38. 38.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  39. 39.In triangle ABC, angle A = 38° and angle B = 33°. What is angle C (in degrees)?
  40. 40.The two interior opposite angles of a triangle are 37° and 53°. What is the exterior angle (in degrees)?

Answer key

  1. 82
  2. 53
  3. 35
  4. 26
  5. 87
  6. No
  7. 31
  8. 38
  9. No
  10. 25
  11. 100
  12. 17
  13. No
  14. 72
  15. 54
  16. 84
  17. Yes
  18. 23
  19. 67
  20. 50
  21. 65
  22. No
  23. 60
  24. 71
  25. 120
  26. 24
  27. 90
  28. 40
  29. 98
  30. 52
  31. 72
  32. 17
  33. 77
  34. 39
  35. 76
  36. 56
  37. 73
  38. 45
  39. 109
  40. 90

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