Question

$39$ persons can build a road in $12$ days, working $5hrs$ a day. In how many days will $30$ persons working $6hrs$ a day, to complete the work?

Answer 1

Given

Number of days required by $39$ persons working $5hrs$ per day $=12days$

Let the required number of days be $x$by $30$ persons working $6hr$ per day

By using indirect proportion
Less number of persons working more days will be required to complete the work

and,
Working more hours per day than in fewer days work will be completed
Therefore,
$$\begin{gathered} 30\times 6\times x=39\times 12\times 5 \\ \Rightarrow x=\frac{39\times 12\times 5}{30\times 6} \\ \Rightarrow x=13days \end{gathered}$$

Hence, $13days$will be required