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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 874 · 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 triangle ABC, angle A = 26° and angle B = 23°. What is angle C (in degrees)?
  2. 2.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  3. 3.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  5. 5.In an isosceles triangle, the two equal angles are 32° each. What is the third angle (in degrees)?
  6. 6.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  7. 7.In triangle ABC, angle A = 38° and angle B = 102°. What is angle C (in degrees)?
  8. 8.The two interior opposite angles of a triangle are 61° and 45°. What is the exterior angle (in degrees)?
  9. 9.Can a triangle have sides of 3 cm, 3 cm and 5 cm? (a) Yes (b) No
  10. 10.In triangle ABC, angle A = 23° and angle B = 128°. What is angle C (in degrees)?
  11. 11.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  12. 12.In a right-angled triangle, one of the other two angles is 27°. What is the third angle (in degrees)?
  13. 13.An exterior angle of a triangle is 104°. One of its two interior opposite angles is 45°. What is the other one (in degrees)?
  14. 14.An exterior angle of a triangle is 153°. One of its two interior opposite angles is 74°. What is the other one (in degrees)?
  15. 15.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  16. 16.Can a triangle have sides of 12 cm, 20 cm and 4 cm? (a) Yes (b) No
  17. 17.In triangle ABC, angle A = 53° and angle B = 54°. What is angle C (in degrees)?
  18. 18.The two interior opposite angles of a triangle are 59° and 75°. What is the exterior angle (in degrees)?
  19. 19.In a right-angled triangle, one of the other two angles is 34°. What is the third angle (in degrees)?
  20. 20.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)?
  21. 21.In a right-angled triangle, one of the other two angles is 59°. What is the third angle (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 81° each. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 33° and angle B = 112°. What is angle C (in degrees)?
  24. 24.Can a triangle have sides of 9 cm, 2 cm and 11 cm? (a) No (b) Yes
  25. 25.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 8 cm, 4 cm and 2 cm? (a) No (b) Yes
  27. 27.In an isosceles triangle, the two equal angles are 25° each. What is the third angle (in degrees)?
  28. 28.An exterior angle of a triangle is 61°. One of its two interior opposite angles is 31°. What is the other one (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 25° and 68°. What is the exterior angle (in degrees)?
  30. 30.Can a triangle have sides of 13 cm, 9 cm and 11 cm? (a) Yes (b) No
  31. 31.The two interior opposite angles of a triangle are 49° and 37°. What is the exterior angle (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  33. 33.In triangle ABC, angle A = 44° and angle B = 21°. What is angle C (in degrees)?
  34. 34.The two interior opposite angles of a triangle are 33° and 40°. What is the exterior angle (in degrees)?
  35. 35.In triangle ABC, angle A = 20° and angle B = 65°. What is angle C (in degrees)?
  36. 36.In triangle ABC, angle A = 94° and angle B = 30°. What is angle C (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 20°. What is the third angle (in degrees)?
  38. 38.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  39. 39.In triangle ABC, angle A = 99° and angle B = 50°. What is angle C (in degrees)?
  40. 40.In triangle ABC, angle A = 70° and angle B = 79°. What is angle C (in degrees)?

Answer key

  1. 131
  2. 41
  3. 50
  4. 100
  5. 116
  6. 90
  7. 40
  8. 106
  9. Yes
  10. 29
  11. 70
  12. 63
  13. 59
  14. 79
  15. 20
  16. No
  17. 73
  18. 134
  19. 56
  20. 7
  21. 31
  22. 18
  23. 35
  24. No
  25. 51
  26. No
  27. 130
  28. 30
  29. 93
  30. Yes
  31. 86
  32. 66
  33. 115
  34. 73
  35. 95
  36. 56
  37. 70
  38. 80
  39. 31
  40. 31

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