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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 65 · 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 = 59° and angle B = 35°. What is angle C (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 27° and 31°. What is the exterior angle (in degrees)?
  3. 3.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  5. 5.An exterior angle of a triangle is 136°. One of its two interior opposite angles is 65°. What is the other one (in degrees)?
  6. 6.In triangle ABC, angle A = 58° and angle B = 40°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 24°. What is the third angle (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 68° each. What is the third angle (in degrees)?
  9. 9.Can a triangle have sides of 2 cm, 11 cm and 16 cm? (a) Yes (b) No
  10. 10.Can a triangle have sides of 6 cm, 7 cm and 2 cm? (a) Yes (b) No
  11. 11.The two interior opposite angles of a triangle are 44° and 34°. What is the exterior angle (in degrees)?
  12. 12.The two interior opposite angles of a triangle are 75° and 28°. What is the exterior angle (in degrees)?
  13. 13.Can a triangle have sides of 2 cm, 8 cm and 8 cm? (a) Yes (b) No
  14. 14.In triangle ABC, angle A = 21° and angle B = 28°. What is angle C (in degrees)?
  15. 15.Can a triangle have sides of 5 cm, 18 cm and 11 cm? (a) No (b) Yes
  16. 16.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  17. 17.An exterior angle of a triangle is 85°. One of its two interior opposite angles is 44°. What is the other one (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 40°. What is the third angle (in degrees)?
  19. 19.In triangle ABC, angle A = 95° and angle B = 64°. What is angle C (in degrees)?
  20. 20.In an isosceles triangle, the angle between the two equal sides is 38°. What is each of the other two angles (in degrees)?
  21. 21.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 9 cm and 12 cm. How long is the longest side (in cm)?
  23. 23.An exterior angle of a triangle is 55°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  24. 24.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  25. 25.Can a triangle have sides of 5 cm, 4 cm and 4 cm? (a) No (b) Yes
  26. 26.In an isosceles triangle, the angle between the two equal sides is 20°. What is each of the other two angles (in degrees)?
  27. 27.In a right-angled triangle, one of the other two angles is 11°. What is the third angle (in degrees)?
  28. 28.In triangle ABC, angle A = 60° and angle B = 30°. What is angle C (in degrees)?
  29. 29.In triangle ABC, angle A = 32° and angle B = 67°. What is angle C (in degrees)?
  30. 30.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)?
  31. 31.Can a triangle have sides of 9 cm, 11 cm and 9 cm? (a) Yes (b) No
  32. 32.In a right-angled triangle, one of the other two angles is 75°. What is the third angle (in degrees)?
  33. 33.An exterior angle of a triangle is 139°. One of its two interior opposite angles is 66°. What is the other one (in degrees)?
  34. 34.The angles of a triangle are in the ratio 1 : 2 : 3. What is the smallest angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 16 cm and 12 cm. How long is the longest side (in cm)?
  37. 37.In an isosceles triangle, the two equal angles are 71° each. What is the third angle (in degrees)?
  38. 38.An exterior angle of a triangle is 97°. One of its two interior opposite angles is 28°. What is the other one (in degrees)?
  39. 39.In triangle ABC, angle A = 59° and angle B = 97°. What is angle C (in degrees)?
  40. 40.An exterior angle of a triangle is 74°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?

Answer key

  1. 86
  2. 58
  3. 43
  4. 60
  5. 71
  6. 82
  7. 66
  8. 44
  9. No
  10. Yes
  11. 78
  12. 103
  13. Yes
  14. 131
  15. No
  16. 63
  17. 41
  18. 50
  19. 21
  20. 71
  21. 50
  22. 15
  23. 34
  24. 57
  25. Yes
  26. 80
  27. 79
  28. 90
  29. 81
  30. 24
  31. Yes
  32. 15
  33. 73
  34. 30
  35. 45
  36. 20
  37. 38
  38. 69
  39. 24
  40. 22

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