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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 451 · 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 57°. One of its two interior opposite angles is 30°. What is the other one (in degrees)?
  2. 2.In an isosceles triangle, the two equal angles are 49° each. What is the third angle (in degrees)?
  3. 3.In triangle ABC, angle A = 85° and angle B = 30°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  5. 5.The two interior opposite angles of a triangle are 61° and 54°. What is the exterior angle (in degrees)?
  6. 6.In triangle ABC, angle A = 88° and angle B = 21°. What is angle C (in degrees)?
  7. 7.In an isosceles triangle, the angle between the two equal sides is 44°. What is each of the other two angles (in degrees)?
  8. 8.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  10. 10.Can a triangle have sides of 7 cm, 3 cm and 11 cm? (a) Yes (b) No
  11. 11.In triangle ABC, angle A = 67° and angle B = 53°. What is angle C (in degrees)?
  12. 12.In triangle ABC, angle A = 92° and angle B = 38°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 70° and angle B = 39°. What is angle C (in degrees)?
  14. 14.Can a triangle have sides of 9 cm, 14 cm and 4 cm? (a) Yes (b) No
  15. 15.Can a triangle have sides of 5 cm, 8 cm and 11 cm? (a) No (b) Yes
  16. 16.The two interior opposite angles of a triangle are 25° and 30°. What is the exterior angle (in degrees)?
  17. 17.Can a triangle have sides of 4 cm, 7 cm and 7 cm? (a) No (b) Yes
  18. 18.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 32° and angle B = 93°. What is angle C (in degrees)?
  20. 20.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 3 : 4 : 5. What is the biggest angle (in degrees)?
  22. 22.In an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  23. 23.The two interior opposite angles of a triangle are 76° and 52°. What is the exterior angle (in degrees)?
  24. 24.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  25. 25.Can a triangle have sides of 8 cm, 9 cm and 20 cm? (a) Yes (b) No
  26. 26.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  27. 27.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)?
  28. 28.In triangle ABC, angle A = 52° and angle B = 27°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 38° and angle B = 49°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 96° and angle B = 63°. What is angle C (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 130°. What is each of the other two angles (in degrees)?
  32. 32.In triangle ABC, angle A = 66° and angle B = 75°. What is angle C (in degrees)?
  33. 33.Can a triangle have sides of 1 cm, 8 cm and 8 cm? (a) No (b) Yes
  34. 34.An exterior angle of a triangle is 125°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  35. 35.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)?
  36. 36.An exterior angle of a triangle is 148°. One of its two interior opposite angles is 73°. What is the other one (in degrees)?
  37. 37.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)?
  38. 38.The two interior opposite angles of a triangle are 57° and 36°. What is the exterior angle (in degrees)?
  39. 39.The longest side of a right-angled triangle is 26 cm and one of the other sides is 10 cm. How long is the third side (in cm)?
  40. 40.In a right-angled triangle, one of the other two angles is 50°. What is the third angle (in degrees)?

Answer key

  1. 27
  2. 82
  3. 65
  4. 36
  5. 115
  6. 71
  7. 68
  8. 90
  9. 51
  10. No
  11. 60
  12. 50
  13. 71
  14. No
  15. Yes
  16. 55
  17. Yes
  18. 100
  19. 55
  20. 20
  21. 75
  22. 19
  23. 128
  24. 20
  25. No
  26. 100
  27. 20
  28. 101
  29. 93
  30. 21
  31. 25
  32. 39
  33. Yes
  34. 79
  35. 24
  36. 75
  37. 15
  38. 93
  39. 24
  40. 40

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