I5.2 If $B$ circular pipes each with an internal diameter of $A \mathrm{~cm}$ carry the same amount of water as a pipe with an internal diameter $6 \mathrm{~cm}$, find $B$.
$\begin{array}{l}\pi(1)^{2} \cdot B=\pi(6)^{2} \\ \Rightarrow B=36\end{array}$