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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 293 · 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 = 53° and angle B = 52°. What is angle C (in degrees)?
  2. 2.The two interior opposite angles of a triangle are 59° and 47°. What is the exterior angle (in degrees)?
  3. 3.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 27° each. What is the third angle (in degrees)?
  5. 5.The longest side of a right-angled triangle is 25 cm and one of the other sides is 24 cm. How long is the third side (in cm)?
  6. 6.In triangle ABC, angle A = 62° and angle B = 84°. What is angle C (in degrees)?
  7. 7.In a right-angled triangle, one of the other two angles is 18°. What is the third angle (in degrees)?
  8. 8.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)?
  9. 9.In triangle ABC, angle A = 63° and angle B = 33°. What is angle C (in degrees)?
  10. 10.The two shorter sides of a right-angled triangle are 3 cm and 4 cm. How long is the longest side (in cm)?
  11. 11.In a right-angled triangle, one of the other two angles is 36°. What is the third angle (in degrees)?
  12. 12.The two shorter sides of a right-angled triangle are 24 cm and 7 cm. How long is the longest side (in cm)?
  13. 13.The longest side of a right-angled triangle is 39 cm and one of the other sides is 15 cm. How long is the third side (in cm)?
  14. 14.In triangle ABC, angle A = 28° and angle B = 98°. What is angle C (in degrees)?
  15. 15.Can a triangle have sides of 13 cm, 6 cm and 3 cm? (a) No (b) Yes
  16. 16.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?
  17. 17.In triangle ABC, angle A = 48° and angle B = 88°. What is angle C (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 22°. What is the third angle (in degrees)?
  19. 19.The two interior opposite angles of a triangle are 48° and 35°. What is the exterior angle (in degrees)?
  20. 20.The longest side of a right-angled triangle is 13 cm and one of the other sides is 12 cm. How long is the third side (in cm)?
  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.In an isosceles triangle, the two equal angles are 58° each. What is the third angle (in degrees)?
  23. 23.In triangle ABC, angle A = 25° and angle B = 108°. What is angle C (in degrees)?
  24. 24.In a right-angled triangle, one of the other two angles is 49°. What is the third angle (in degrees)?
  25. 25.In an isosceles triangle, the angle between the two equal sides is 126°. What is each of the other two angles (in degrees)?
  26. 26.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)?
  27. 27.Can a triangle have sides of 7 cm, 13 cm and 8 cm? (a) Yes (b) No
  28. 28.In a right-angled triangle, one of the other two angles is 64°. What is the third angle (in degrees)?
  29. 29.Can a triangle have sides of 22 cm, 9 cm and 10 cm? (a) Yes (b) No
  30. 30.In a right-angled triangle, one of the other two angles is 10°. What is the third angle (in degrees)?
  31. 31.In triangle ABC, angle A = 54° and angle B = 61°. What is angle C (in degrees)?
  32. 32.In triangle ABC, angle A = 41° and angle B = 63°. What is angle C (in degrees)?
  33. 33.An exterior angle of a triangle is 112°. One of its two interior opposite angles is 36°. What is the other one (in degrees)?
  34. 34.In an isosceles triangle, the angle between the two equal sides is 60°. What is each of the other two angles (in degrees)?
  35. 35.In an isosceles triangle, the two equal angles are 21° each. What is the third angle (in degrees)?
  36. 36.Can a triangle have sides of 12 cm, 5 cm and 5 cm? (a) Yes (b) No
  37. 37.The two shorter sides of a right-angled triangle are 12 cm and 5 cm. How long is the longest side (in cm)?
  38. 38.In an isosceles triangle, the two equal angles are 48° each. What is the third angle (in degrees)?
  39. 39.Can a triangle have sides of 9 cm, 24 cm and 10 cm? (a) No (b) Yes
  40. 40.Can a triangle have sides of 12 cm, 23 cm and 10 cm? (a) No (b) Yes

Answer key

  1. 75
  2. 106
  3. 45
  4. 126
  5. 7
  6. 34
  7. 72
  8. 12
  9. 84
  10. 5
  11. 54
  12. 25
  13. 36
  14. 54
  15. No
  16. 59
  17. 44
  18. 68
  19. 83
  20. 5
  21. 25
  22. 64
  23. 47
  24. 41
  25. 27
  26. 24
  27. Yes
  28. 26
  29. No
  30. 80
  31. 65
  32. 76
  33. 76
  34. 60
  35. 138
  36. No
  37. 13
  38. 84
  39. No
  40. No

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