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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 1 · 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 45°. What is the third angle (in degrees)?
  2. 2.Can a triangle have sides of 10 cm, 12 cm and 10 cm? (a) Yes (b) No
  3. 3.In an isosceles triangle, the angle between the two equal sides is 54°. What is each of the other two angles (in degrees)?
  4. 4.In an isosceles triangle, the angle between the two equal sides is 118°. What is each of the other two angles (in degrees)?
  5. 5.Can a triangle have sides of 5 cm, 4 cm and 2 cm? (a) No (b) Yes
  6. 6.In a right-angled triangle, one of the other two angles is 67°. What is the third angle (in degrees)?
  7. 7.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  8. 8.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 76°. What is the third angle (in degrees)?
  10. 10.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)?
  11. 11.Can a triangle have sides of 12 cm, 5 cm and 15 cm? (a) Yes (b) No
  12. 12.In triangle ABC, angle A = 77° and angle B = 61°. What is angle C (in degrees)?
  13. 13.In triangle ABC, angle A = 37° and angle B = 25°. What is angle C (in degrees)?
  14. 14.In triangle ABC, angle A = 35° and angle B = 23°. What is angle C (in degrees)?
  15. 15.In a right-angled triangle, one of the other two angles is 47°. What is the third angle (in degrees)?
  16. 16.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)?
  17. 17.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  18. 18.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  19. 19.In an isosceles triangle, the two equal angles are 34° each. What is the third angle (in degrees)?
  20. 20.Can a triangle have sides of 6 cm, 16 cm and 6 cm? (a) Yes (b) No
  21. 21.An exterior angle of a triangle is 88°. One of its two interior opposite angles is 55°. What is the other one (in degrees)?
  22. 22.The angles of a triangle are in the ratio 5 : 6 : 7. What is the smallest angle (in degrees)?
  23. 23.Can a triangle have sides of 11 cm, 3 cm and 11 cm? (a) No (b) Yes
  24. 24.The two interior opposite angles of a triangle are 71° and 80°. What is the exterior angle (in degrees)?
  25. 25.In triangle ABC, angle A = 72° and angle B = 49°. What is angle C (in degrees)?
  26. 26.In a right-angled triangle, one of the other two angles is 63°. What is the third angle (in degrees)?
  27. 27.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  28. 28.The angles of a triangle are in the ratio 1 : 2 : 3. What is the biggest angle (in degrees)?
  29. 29.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  30. 30.An exterior angle of a triangle is 110°. One of its two interior opposite angles is 56°. What is the other one (in degrees)?
  31. 31.In an isosceles triangle, the angle between the two equal sides is 92°. What is each of the other two angles (in degrees)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 124°. What is each of the other two angles (in degrees)?
  33. 33.The two interior opposite angles of a triangle are 65° and 64°. What is the exterior angle (in degrees)?
  34. 34.An exterior angle of a triangle is 105°. One of its two interior opposite angles is 25°. What is the other one (in degrees)?
  35. 35.The two interior opposite angles of a triangle are 29° and 79°. What is the exterior angle (in degrees)?
  36. 36.An exterior angle of a triangle is 106°. One of its two interior opposite angles is 40°. What is the other one (in degrees)?
  37. 37.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  38. 38.Can a triangle have sides of 4 cm, 2 cm and 3 cm? (a) No (b) Yes
  39. 39.In a right-angled triangle, one of the other two angles is 19°. What is the third angle (in degrees)?
  40. 40.In triangle ABC, angle A = 100° and angle B = 24°. What is angle C (in degrees)?

Answer key

  1. 45
  2. Yes
  3. 63
  4. 31
  5. Yes
  6. 23
  7. 70
  8. 64
  9. 14
  10. 24
  11. Yes
  12. 42
  13. 118
  14. 122
  15. 43
  16. 12
  17. 12
  18. 78
  19. 112
  20. No
  21. 33
  22. 50
  23. Yes
  24. 151
  25. 59
  26. 27
  27. 80
  28. 90
  29. 16
  30. 54
  31. 44
  32. 28
  33. 129
  34. 80
  35. 108
  36. 66
  37. 60
  38. Yes
  39. 71
  40. 56

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