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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 390 · 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 = 27° and angle B = 31°. What is angle C (in degrees)?
  2. 2.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  3. 3.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 59°. What is the other one (in degrees)?
  4. 4.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  5. 5.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 61° each. What is the third angle (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  8. 8.In triangle ABC, angle A = 40° and angle B = 112°. What is angle C (in degrees)?
  9. 9.An exterior angle of a triangle is 144°. One of its two interior opposite angles is 69°. What is the other one (in degrees)?
  10. 10.In triangle ABC, angle A = 94° and angle B = 21°. What is angle C (in degrees)?
  11. 11.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  12. 12.Can a triangle have sides of 11 cm, 7 cm and 2 cm? (a) Yes (b) No
  13. 13.The two interior opposite angles of a triangle are 49° and 52°. What is the exterior angle (in degrees)?
  14. 14.An exterior angle of a triangle is 75°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 52°. What is the third angle (in degrees)?
  16. 16.An exterior angle of a triangle is 100°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  17. 17.The angles of a triangle are in the ratio 2 : 3 : 4. What is the smallest angle (in degrees)?
  18. 18.The longest side of a right-angled triangle is 17 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  19. 19.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 51°. What is the third angle (in degrees)?
  21. 21.The angles of a triangle are in the ratio 1 : 2 : 2. What is the smallest angle (in degrees)?
  22. 22.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)?
  23. 23.Can a triangle have sides of 21 cm, 9 cm and 9 cm? (a) No (b) Yes
  24. 24.In triangle ABC, angle A = 28° and angle B = 96°. What is angle C (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 41° each. What is the third angle (in degrees)?
  26. 26.Can a triangle have sides of 13 cm, 6 cm and 5 cm? (a) Yes (b) No
  27. 27.In an isosceles triangle, the angle between the two equal sides is 58°. What is each of the other two angles (in degrees)?
  28. 28.In triangle ABC, angle A = 20° and angle B = 48°. What is angle C (in degrees)?
  29. 29.The two interior opposite angles of a triangle are 69° and 34°. What is the exterior angle (in degrees)?
  30. 30.Can a triangle have sides of 5 cm, 12 cm and 12 cm? (a) Yes (b) No
  31. 31.In a right-angled triangle, one of the other two angles is 44°. What is the third angle (in degrees)?
  32. 32.Can a triangle have sides of 4 cm, 7 cm and 9 cm? (a) Yes (b) No
  33. 33.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 42° each. What is the third angle (in degrees)?
  36. 36.In triangle ABC, angle A = 43° and angle B = 33°. What is angle C (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  38. 38.An exterior angle of a triangle is 133°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  39. 39.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  40. 40.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?

Answer key

  1. 122
  2. 36
  3. 39
  4. 47
  5. 69
  6. 58
  7. 80
  8. 28
  9. 75
  10. 65
  11. 48
  12. No
  13. 101
  14. 50
  15. 38
  16. 66
  17. 40
  18. 8
  19. 100
  20. 39
  21. 36
  22. 7
  23. No
  24. 56
  25. 98
  26. No
  27. 61
  28. 112
  29. 103
  30. Yes
  31. 46
  32. Yes
  33. 45
  34. 53
  35. 96
  36. 104
  37. 41
  38. 72
  39. 17
  40. 36

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