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Class 7 Maths Worksheet: Triangles

Maths worksheets lesson 53: Triangles: angle sum, exterior angle and Pythagoras · Set 93 · 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.The two shorter sides of a right-angled triangle are 7 cm and 24 cm. How long is the longest side (in cm)?
  2. 2.In triangle ABC, angle A = 63° and angle B = 48°. What is angle C (in degrees)?
  3. 3.The angles of a triangle are in the ratio 2 : 3 : 5. What is the smallest angle (in degrees)?
  4. 4.In an isosceles triangle, the two equal angles are 36° 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 7 cm. How long is the third side (in cm)?
  6. 6.An exterior angle of a triangle is 101°. One of its two interior opposite angles is 33°. What is the other one (in degrees)?
  7. 7.The angles of a triangle are in the ratio 2 : 3 : 4. What is the biggest angle (in degrees)?
  8. 8.The angles of a triangle are in the ratio 3 : 4 : 5. What is the smallest angle (in degrees)?
  9. 9.Can a triangle have sides of 9 cm, 11 cm and 24 cm? (a) No (b) Yes
  10. 10.The angles of a triangle are in the ratio 5 : 6 : 7. What is the biggest angle (in degrees)?
  11. 11.Can a triangle have sides of 7 cm, 7 cm and 5 cm? (a) Yes (b) No
  12. 12.Can a triangle have sides of 7 cm, 8 cm and 11 cm? (a) No (b) Yes
  13. 13.An exterior angle of a triangle is 134°. One of its two interior opposite angles is 63°. What is the other one (in degrees)?
  14. 14.An exterior angle of a triangle is 77°. One of its two interior opposite angles is 21°. What is the other one (in degrees)?
  15. 15.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)?
  16. 16.The two interior opposite angles of a triangle are 20° and 44°. What is the exterior angle (in degrees)?
  17. 17.The angles of a triangle are in the ratio 1 : 1 : 2. What is the smallest angle (in degrees)?
  18. 18.In a right-angled triangle, one of the other two angles is 66°. What is the third angle (in degrees)?
  19. 19.An exterior angle of a triangle is 117°. One of its two interior opposite angles is 46°. What is the other one (in degrees)?
  20. 20.In triangle ABC, angle A = 33° and angle B = 77°. What is angle C (in degrees)?
  21. 21.The two interior opposite angles of a triangle are 49° and 22°. What is the exterior angle (in degrees)?
  22. 22.An exterior angle of a triangle is 122°. One of its two interior opposite angles is 49°. What is the other one (in degrees)?
  23. 23.The angles of a triangle are in the ratio 3 : 3 : 4. What is the biggest angle (in degrees)?
  24. 24.In triangle ABC, angle A = 37° and angle B = 53°. What is angle C (in degrees)?
  25. 25.In a right-angled triangle, one of the other two angles is 30°. What is the third angle (in degrees)?
  26. 26.In an isosceles triangle, the angle between the two equal sides is 132°. What is each of the other two angles (in degrees)?
  27. 27.The two shorter sides of a right-angled triangle are 15 cm and 8 cm. How long is the longest side (in cm)?
  28. 28.In triangle ABC, angle A = 29° and angle B = 118°. What is angle C (in degrees)?
  29. 29.Can a triangle have sides of 11 cm, 12 cm and 2 cm? (a) Yes (b) No
  30. 30.In triangle ABC, angle A = 76° and angle B = 81°. What is angle C (in degrees)?
  31. 31.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)?
  32. 32.The angles of a triangle are in the ratio 2 : 2 : 5. What is the biggest angle (in degrees)?
  33. 33.In an isosceles triangle, the angle between the two equal sides is 68°. What is each of the other two angles (in degrees)?
  34. 34.In a right-angled triangle, one of the other two angles is 45°. What is the third angle (in degrees)?
  35. 35.In triangle ABC, angle A = 39° and angle B = 59°. What is angle C (in degrees)?
  36. 36.In a right-angled triangle, one of the other two angles is 37°. What is the third angle (in degrees)?
  37. 37.Can a triangle have sides of 7 cm, 7 cm and 11 cm? (a) No (b) Yes
  38. 38.In triangle ABC, angle A = 61° and angle B = 92°. What is angle C (in degrees)?
  39. 39.Can a triangle have sides of 3 cm, 4 cm and 3 cm? (a) No (b) Yes
  40. 40.In a right-angled triangle, one of the other two angles is 31°. What is the third angle (in degrees)?

Answer key

  1. 25
  2. 69
  3. 36
  4. 108
  5. 24
  6. 68
  7. 80
  8. 45
  9. No
  10. 70
  11. Yes
  12. Yes
  13. 71
  14. 56
  15. 5
  16. 64
  17. 45
  18. 24
  19. 71
  20. 70
  21. 71
  22. 73
  23. 72
  24. 90
  25. 60
  26. 24
  27. 17
  28. 33
  29. Yes
  30. 23
  31. 4
  32. 100
  33. 56
  34. 45
  35. 82
  36. 53
  37. Yes
  38. 27
  39. Yes
  40. 59

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