Question
If $15$ workers can build a wall in $48$ hours, how many workers will be required to do the same work in $30$ hours?
Number of hours $48$ $30$
Number of workers $15$ $y$

Answer

It is given the number of workers employed to build the wall in $30$ hours be $y$
Obviously more the number of workers, faster will they build the wall.
so, the number of hours and number of workers vary in inverse proportion.
So $48$ $\times$ $15 = 30$ $\times$ $y$
$y =$ $\frac{48 \times 15}{30}$ or $y = 24$
i.e., to finish the work in $30$ hours, $24$ workers are required.

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