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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 554 · 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 = 94° and angle B = 25°. What is angle C (in degrees)?
  2. 2.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 67°. What is the other one (in degrees)?
  3. 3.In triangle ABC, angle A = 98° and angle B = 40°. What is angle C (in degrees)?
  4. 4.The angles of a triangle are in the ratio 2 : 3 : 5. What is the biggest angle (in degrees)?
  5. 5.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  6. 6.In triangle ABC, angle A = 35° and angle B = 124°. What is angle C (in degrees)?
  7. 7.The angles of a triangle are in the ratio 4 : 5 : 6. What is the biggest angle (in degrees)?
  8. 8.The longest side of a right-angled triangle is 25 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  9. 9.In triangle ABC, angle A = 20° and angle B = 22°. What is angle C (in degrees)?
  10. 10.In a right-angled triangle, one of the other two angles is 74°. What is the third angle (in degrees)?
  11. 11.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  12. 12.An exterior angle of a triangle is 128°. One of its two interior opposite angles is 61°. What is the other one (in degrees)?
  13. 13.Can a triangle have sides of 5 cm, 5 cm and 12 cm? (a) Yes (b) No
  14. 14.The two interior opposite angles of a triangle are 68° and 34°. What is the exterior angle (in degrees)?
  15. 15.In triangle ABC, angle A = 58° and angle B = 52°. What is angle C (in degrees)?
  16. 16.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  17. 17.In triangle ABC, angle A = 20° and angle B = 70°. What is angle C (in degrees)?
  18. 18.Can a triangle have sides of 5 cm, 12 cm and 4 cm? (a) Yes (b) No
  19. 19.In triangle ABC, angle A = 83° and angle B = 36°. What is angle C (in degrees)?
  20. 20.In a right-angled triangle, one of the other two angles is 48°. What is the third angle (in degrees)?
  21. 21.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  22. 22.The two interior opposite angles of a triangle are 23° and 66°. What is the exterior angle (in degrees)?
  23. 23.An exterior angle of a triangle is 127°. One of its two interior opposite angles is 70°. What is the other one (in degrees)?
  24. 24.In an isosceles triangle, the two equal angles are 37° each. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the two equal angles are 51° each. What is the third angle (in degrees)?
  26. 26.The two shorter sides of a right-angled triangle are 10 cm and 24 cm. How long is the longest side (in cm)?
  27. 27.In an isosceles triangle, the two equal angles are 30° each. What is the third angle (in degrees)?
  28. 28.Can a triangle have sides of 6 cm, 5 cm and 3 cm? (a) No (b) Yes
  29. 29.In triangle ABC, angle A = 28° and angle B = 20°. What is angle C (in degrees)?
  30. 30.In triangle ABC, angle A = 36° and angle B = 70°. What is angle C (in degrees)?
  31. 31.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)?
  32. 32.In an isosceles triangle, the angle between the two equal sides is 152°. What is each of the other two angles (in degrees)?
  33. 33.The angles of a triangle are in the ratio 1 : 4 : 5. What is the biggest angle (in degrees)?
  34. 34.Can a triangle have sides of 5 cm, 5 cm and 6 cm? (a) No (b) Yes
  35. 35.The two interior opposite angles of a triangle are 26° and 78°. What is the exterior angle (in degrees)?
  36. 36.Can a triangle have sides of 12 cm, 7 cm and 23 cm? (a) No (b) Yes
  37. 37.Can a triangle have sides of 3 cm, 2 cm and 9 cm? (a) No (b) Yes
  38. 38.In triangle ABC, angle A = 20° and angle B = 69°. What is angle C (in degrees)?
  39. 39.Can a triangle have sides of 11 cm, 4 cm and 13 cm? (a) Yes (b) No
  40. 40.In triangle ABC, angle A = 72° and angle B = 58°. What is angle C (in degrees)?

Answer key

  1. 61
  2. 34
  3. 42
  4. 90
  5. 70
  6. 21
  7. 72
  8. 20
  9. 138
  10. 16
  11. 126
  12. 67
  13. No
  14. 102
  15. 70
  16. 49
  17. 90
  18. No
  19. 61
  20. 42
  21. 25
  22. 89
  23. 57
  24. 106
  25. 78
  26. 26
  27. 120
  28. Yes
  29. 132
  30. 74
  31. 24
  32. 14
  33. 90
  34. Yes
  35. 104
  36. No
  37. No
  38. 91
  39. Yes
  40. 50

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