A certain number of men can complete a piece of work in 6k days, where k is a natural number. By what…
A certain number of men can complete a piece of work in 6k days, where k is a natural number. By what percent should the number of men be increased so that the work can be completed in 5k days?
10%
(50/3)%
20%
25%
Solution
Let the number of men in the first and second cases be $m$ and $n$. Man-days are constant: $6k \times m = 5k \times n$, so $6m = 5n$, giving $n = (6/5)m = 1.2m = m + 20\%$ of $m$. Hence the number of men must be increased by 20%.