Answer :

(5/125)x100 = percentage = 4%

[tex]\begin{array}{ccc}125&-&100\%\\5&-&x\%\end{array}\ \ \ \ |cross\ multiply\\\\125\cdot x=5\cdot100\\125x=500\ \ \ \ |divide\ both\ sides\ by\ 125\\\boxed{x=4\ (\%)}[/tex]