Casting — How many spherical bullets (diameter 2 cm) can be made from a lead cube of edge 22 cm?

Difficulty: Medium

Correct Answer: 2541

Explanation:


Introduction / Context:
When recasting, volume is conserved. Number of bullets = (volume of cube) / (volume of one bullet). Use exact π = 22/7 for clean integers here.



Given Data / Assumptions:

  • Cube edge a = 22 cm ⇒ V_cube = a^3 = 10648 cm^3
  • Bullet diameter = 2 cm ⇒ radius = 1 cm
  • Sphere volume V_s = (4/3)πr^3


Concept / Approach:
Compute V_s with r = 1 using π = 22/7, then divide the cube volume by V_s and take the integer count.



Step-by-Step Solution:
V_s = (4/3) * (22/7) * 1^3 = 88/21 cm^3N = 10648 / (88/21) = (10648 * 21) / 88 = 121 * 21 = 2541



Verification / Alternative check:
88 * 121 = 10648, so cancellation is exact.



Why Other Options Are Wrong:
2662 and 1347 come from rounding with π = 3.14; 5324 doubles the correct count.



Common Pitfalls:
Using diameter instead of radius in sphere volume; forgetting exact fraction 22/7.



Final Answer:
2541

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