A road contractor is being hired to fix up roads in a county for 20 days. The contractor hires 15 men to finish this. How many days will he take if hires 30 men ?

Question

$\begin{array}{1 1} (a)\; \text{10 days} \\ (b)\; \text{15 days} \\ (c)\; \text{9 days} \\ (d) \; \text{5 days} \end{array}$