Question

How many spherical bullets can be made out of a lead cylinder $15$cm high and with base radius $3$cm, each bullet being $5$mm in diameter?

• A. $6000$
• B. $6480$
• C. $7260$
• D. $7800$

Answer 1

Answer: (B)

$6480$

Volume of cylinder $V=\pi r^{2}h=9\times 15\pi =135\pi$

Volume of bullet $v=\frac{4}{3}\pi r^3=\frac{4}{3}\times {2.5}^3\times {10}^{-3}\pi$

Number of bullets $=\frac{V}{v}=\frac{135\pi \times {10}^3\times 3}{4\times {2.5}^3\times \pi }=6480$