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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 472 · 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 a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  2. 2.In triangle ABC, angle A = 91° and angle B = 61°. What is angle C (in degrees)?
  3. 3.In an isosceles triangle, the two equal angles are 31° each. What is the third angle (in degrees)?
  4. 4.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  5. 5.Can a triangle have sides of 10 cm, 7 cm and 8 cm? (a) Yes (b) No
  6. 6.In an isosceles triangle, the two equal angles are 57° each. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 1 : 3 : 5. What is the biggest angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  9. 9.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  10. 10.The two interior opposite angles of a triangle are 50° and 55°. What is the exterior angle (in degrees)?
  11. 11.In an isosceles triangle, the angle between the two equal sides is 160°. What is each of the other two angles (in degrees)?
  12. 12.In an isosceles triangle, the angle between the two equal sides is 78°. What is each of the other two angles (in degrees)?
  13. 13.Can a triangle have sides of 2 cm, 2 cm and 2 cm? (a) Yes (b) No
  14. 14.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  15. 15.The longest side of a right-angled triangle is 13 cm and one of the other sides is 5 cm. How long is the third side (in cm)?
  16. 16.In triangle ABC, angle A = 57° and angle B = 54°. What is angle C (in degrees)?
  17. 17.An exterior angle of a triangle is 43°. One of its two interior opposite angles is 23°. What is the other one (in degrees)?
  18. 18.Can a triangle have sides of 5 cm, 4 cm and 2 cm? (a) No (b) Yes
  19. 19.An exterior angle of a triangle is 73°. One of its two interior opposite angles is 53°. What is the other one (in degrees)?
  20. 20.In triangle ABC, angle A = 41° and angle B = 112°. What is angle C (in degrees)?
  21. 21.Can a triangle have sides of 10 cm, 23 cm and 9 cm? (a) No (b) Yes
  22. 22.Can a triangle have sides of 15 cm, 12 cm and 7 cm? (a) No (b) Yes
  23. 23.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  24. 24.In triangle ABC, angle A = 50° and angle B = 22°. What is angle C (in degrees)?
  25. 25.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 43°. What is the third angle (in degrees)?
  27. 27.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  28. 28.In triangle ABC, angle A = 21° and angle B = 103°. What is angle C (in degrees)?
  29. 29.The longest side of a right-angled triangle is 30 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  30. 30.The angles of a triangle are in the ratio 3 : 5 : 7. What is the smallest angle (in degrees)?
  31. 31.In triangle ABC, angle A = 46° and angle B = 99°. What is angle C (in degrees)?
  32. 32.The longest side of a right-angled triangle is 10 cm and one of the other sides is 6 cm. How long is the third side (in cm)?
  33. 33.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  34. 34.In an isosceles triangle, the two equal angles are 64° each. What is the third angle (in degrees)?
  35. 35.The angles of a triangle are in the ratio 4 : 5 : 6. What is the smallest angle (in degrees)?
  36. 36.The two shorter sides of a right-angled triangle are 15 cm and 20 cm. How long is the longest side (in cm)?
  37. 37.An exterior angle of a triangle is 99°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  38. 38.Can a triangle have sides of 17 cm, 10 cm and 6 cm? (a) No (b) Yes
  39. 39.The two interior opposite angles of a triangle are 79° and 49°. What is the exterior angle (in degrees)?
  40. 40.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 39°. What is the other one (in degrees)?

Answer key

  1. 23
  2. 28
  3. 118
  4. 46
  5. Yes
  6. 66
  7. 100
  8. 72
  9. 90
  10. 105
  11. 10
  12. 51
  13. Yes
  14. 72
  15. 12
  16. 69
  17. 20
  18. Yes
  19. 20
  20. 27
  21. No
  22. Yes
  23. 90
  24. 108
  25. 80
  26. 47
  27. 31
  28. 56
  29. 18
  30. 36
  31. 35
  32. 8
  33. 34
  34. 52
  35. 48
  36. 25
  37. 29
  38. No
  39. 128
  40. 71

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