A man undertakes to do a certain work in 150 days. He employs 200 men. He finds that only a quarter of the work is done in 50 days. The number of additional men that should be appointed so that the whole work will be finished in time is = ?

Let 'n' number of men can required
$$\eqalign{ & \frac{{\left( {{{200}_{{\text{men}}}} \times {{50}_{{\text{days}}}}} \right)}}{{\frac{1}{4}}} = \frac{{\left( {200 + {\text{n}}} \right) \times {{100}_{{\text{days}}}}}}{{\frac{3}{4}}} \cr & \Rightarrow 3 \times 100 = \left( {200 + {\text{n}}} \right) \cr & \Rightarrow {\text{n}} = 100 \cr} $$