You are given marbles of diameter 10mm.They are to be placed such their centres are lying in a square bond by four lines each of length 40mm.What will be the arrangement of marbles in a plane so that maximum number of marbles can be placed inside the area?Derive the expression for the number of molecules per unit area.

Question

$\begin{array}{1 1}1.125\\2.125\\3.125\\4.125\end{array}$