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?

Answer 1

$\begin{array}{ccc}\text{No. of workers(N)}& 15& x\\ \text{time in hours(T)}& 48& 30\end{array}$

The relation between No. of workers(N) and time required (T) is Indirect proportion.

i.e, $T\propto \frac{1}{N}$

$\therefore T\times N=constant$

$\therefore 15\times 48=x\times 30$

$\Rightarrow x=\frac{15\times 48}{30}$

$\therefore x=24$

Hence, $24$ workers will complete the work in $30$ hours.

OR,

In $48$ hrs, the wall is built by $15$ workers

Thus, in $30$ hrs, the wall will be built by $\frac{15\times 48}{30}$ workers

$=24$ workers