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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 477 · 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 an isosceles triangle, the angle between the two equal sides is 142°. What is each of the other two angles (in degrees)?
  2. 2.In triangle ABC, angle A = 91° and angle B = 44°. What is angle C (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 3 : 5. What is the smallest angle (in degrees)?
  4. 4.In a right-angled triangle, one of the other two angles is 39°. What is the third angle (in degrees)?
  5. 5.In triangle ABC, angle A = 37° and angle B = 21°. What is angle C (in degrees)?
  6. 6.In an isosceles triangle, the two equal angles are 78° each. What is the third angle (in degrees)?
  7. 7.Can a triangle have sides of 5 cm, 4 cm and 5 cm? (a) No (b) Yes
  8. 8.In an isosceles triangle, the angle between the two equal sides is 94°. What is each of the other two angles (in degrees)?
  9. 9.Can a triangle have sides of 19 cm, 3 cm and 12 cm? (a) Yes (b) No
  10. 10.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)?
  11. 11.The angles of a triangle are in the ratio 2 : 7 : 9. What is the smallest angle (in degrees)?
  12. 12.In triangle ABC, angle A = 59° and angle B = 54°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 43° and angle B = 106°. What is angle C (in degrees)?
  14. 14.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  15. 15.In an isosceles triangle, the two equal angles are 28° each. What is the third angle (in degrees)?
  16. 16.In a right-angled triangle, one of the other two angles is 55°. What is the third angle (in degrees)?
  17. 17.An exterior angle of a triangle is 108°. One of its two interior opposite angles is 47°. What is the other one (in degrees)?
  18. 18.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  19. 19.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  20. 20.An exterior angle of a triangle is 98°. One of its two interior opposite angles is 57°. What is the other one (in degrees)?
  21. 21.In an isosceles triangle, the angle between the two equal sides is 30°. What is each of the other two angles (in degrees)?
  22. 22.In an isosceles triangle, the two equal angles are 79° each. What is the third angle (in degrees)?
  23. 23.An exterior angle of a triangle is 84°. One of its two interior opposite angles is 34°. What is the other one (in degrees)?
  24. 24.Can a triangle have sides of 12 cm, 7 cm and 8 cm? (a) No (b) Yes
  25. 25.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  26. 26.Can a triangle have sides of 7 cm, 4 cm and 5 cm? (a) Yes (b) No
  27. 27.The two interior opposite angles of a triangle are 74° and 54°. What is the exterior angle (in degrees)?
  28. 28.In a right-angled triangle, one of the other two angles is 12°. What is the third angle (in degrees)?
  29. 29.In an isosceles triangle, the angle between the two equal sides is 42°. What is each of the other two angles (in degrees)?
  30. 30.In triangle ABC, angle A = 39° and angle B = 90°. What is angle C (in degrees)?
  31. 31.The angles of a triangle are in the ratio 1 : 2 : 6. What is the smallest angle (in degrees)?
  32. 32.Can a triangle have sides of 10 cm, 7 cm and 18 cm? (a) No (b) Yes
  33. 33.Can a triangle have sides of 5 cm, 5 cm and 2 cm? (a) Yes (b) No
  34. 34.The angles of a triangle are in the ratio 3 : 5 : 7. What is the biggest angle (in degrees)?
  35. 35.In a right-angled triangle, one of the other two angles is 42°. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 5 cm, 7 cm and 4 cm? (a) Yes (b) No
  37. 37.The two interior opposite angles of a triangle are 64° and 34°. What is the exterior angle (in degrees)?
  38. 38.Can a triangle have sides of 5 cm, 5 cm and 13 cm? (a) No (b) Yes
  39. 39.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 65° and angle B = 84°. What is angle C (in degrees)?

Answer key

  1. 19
  2. 45
  3. 20
  4. 51
  5. 122
  6. 24
  7. Yes
  8. 43
  9. No
  10. 24
  11. 20
  12. 67
  13. 31
  14. 70
  15. 124
  16. 35
  17. 61
  18. 5
  19. 68
  20. 41
  21. 75
  22. 22
  23. 50
  24. Yes
  25. 35
  26. Yes
  27. 128
  28. 78
  29. 69
  30. 51
  31. 20
  32. No
  33. Yes
  34. 84
  35. 48
  36. Yes
  37. 98
  38. No
  39. 72
  40. 31

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