The amount of work in a leather factory is increased by 50%. By what percent is it necessary to increase the number of workers to complete the new amount of work in previously planned time, if the productivity of the new labour is 25% more.

Men × Time = Work
100 × 1 = 100 unit work
150 × 1 = 150 unit work
Extra man power = 50
But since, new workers are $$\frac{5}{4}$$ time as efficient as existing workers
Thus,
Actual no. of workers = $$\frac{{50}}{{\frac{5}{4}}}$$ = 40 workers
% required = $$\frac{{40 \times 100}}{{100}} = 40\% $$