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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 819 · 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 39°. What is the third angle (in degrees)?
  2. 2.In an isosceles triangle, the angle between the two equal sides is 48°. What is each of the other two angles (in degrees)?
  3. 3.In triangle ABC, angle A = 95° and angle B = 26°. What is angle C (in degrees)?
  4. 4.In triangle ABC, angle A = 85° and angle B = 61°. What is angle C (in degrees)?
  5. 5.Can a triangle have sides of 11 cm, 10 cm and 5 cm? (a) No (b) Yes
  6. 6.In an isosceles triangle, the angle between the two equal sides is 62°. What is each of the other two angles (in degrees)?
  7. 7.In triangle ABC, angle A = 65° and angle B = 77°. What is angle C (in degrees)?
  8. 8.In triangle ABC, angle A = 34° and angle B = 52°. What is angle C (in degrees)?
  9. 9.In a right-angled triangle, one of the other two angles is 16°. What is the third angle (in degrees)?
  10. 10.In triangle ABC, angle A = 50° and angle B = 34°. What is angle C (in degrees)?
  11. 11.Can a triangle have sides of 13 cm, 12 cm and 4 cm? (a) No (b) Yes
  12. 12.In triangle ABC, angle A = 65° and angle B = 25°. What is angle C (in degrees)?
  13. 13.The longest side of a right-angled triangle is 5 cm and one of the other sides is 3 cm. How long is the third side (in cm)?
  14. 14.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  15. 15.The longest side of a right-angled triangle is 20 cm and one of the other sides is 16 cm. How long is the third side (in cm)?
  16. 16.Can a triangle have sides of 9 cm, 2 cm and 16 cm? (a) No (b) Yes
  17. 17.In an isosceles triangle, the angle between the two equal sides is 136°. What is each of the other two angles (in degrees)?
  18. 18.An exterior angle of a triangle is 137°. One of its two interior opposite angles is 75°. What is the other one (in degrees)?
  19. 19.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)?
  20. 20.In triangle ABC, angle A = 67° and angle B = 68°. What is angle C (in degrees)?
  21. 21.An exterior angle of a triangle is 49°. One of its two interior opposite angles is 27°. What is the other one (in degrees)?
  22. 22.The two shorter sides of a right-angled triangle are 15 cm and 36 cm. How long is the longest side (in cm)?
  23. 23.In triangle ABC, angle A = 100° and angle B = 36°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 13°. What is the third angle (in degrees)?
  25. 25.Can a triangle have sides of 4 cm, 4 cm and 7 cm? (a) Yes (b) No
  26. 26.In triangle ABC, angle A = 27° and angle B = 25°. What is angle C (in degrees)?
  27. 27.The angles of a triangle are in the ratio 1 : 2 : 6. What is the biggest angle (in degrees)?
  28. 28.In triangle ABC, angle A = 50° and angle B = 77°. What is angle C (in degrees)?
  29. 29.In an isosceles triangle, the two equal angles are 84° each. What is the third angle (in degrees)?
  30. 30.The angles of a triangle are in the ratio 1 : 4 : 5. What is the smallest angle (in degrees)?
  31. 31.In triangle ABC, angle A = 37° and angle B = 39°. What is angle C (in degrees)?
  32. 32.In an isosceles triangle, the two equal angles are 40° each. What is the third angle (in degrees)?
  33. 33.An exterior angle of a triangle is 120°. One of its two interior opposite angles is 52°. What is the other one (in degrees)?
  34. 34.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  35. 35.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  36. 36.The angles of a triangle are in the ratio 1 : 1 : 2. What is the biggest angle (in degrees)?
  37. 37.In triangle ABC, angle A = 73° and angle B = 52°. What is angle C (in degrees)?
  38. 38.In triangle ABC, angle A = 66° and angle B = 35°. What is angle C (in degrees)?
  39. 39.The angles of a triangle are in the ratio 2 : 2 : 5. What is the smallest angle (in degrees)?
  40. 40.In an isosceles triangle, the angle between the two equal sides is 86°. What is each of the other two angles (in degrees)?

Answer key

  1. 51
  2. 66
  3. 59
  4. 34
  5. Yes
  6. 59
  7. 38
  8. 94
  9. 74
  10. 96
  11. Yes
  12. 90
  13. 4
  14. 45
  15. 12
  16. No
  17. 22
  18. 62
  19. 12
  20. 45
  21. 22
  22. 39
  23. 44
  24. 77
  25. Yes
  26. 128
  27. 120
  28. 53
  29. 12
  30. 18
  31. 104
  32. 100
  33. 68
  34. 36
  35. 13
  36. 90
  37. 55
  38. 79
  39. 40
  40. 47

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