Question

Given that $15$ workers can build a wall in $48$ hours. How many workers will be required to do the same work in $30$ hours?
[2 marks]

Answer 1

Let the number of workers employed to build the wall in $30$ hours be $y$.

Number of hours	$48$	$30$
Number of workers	$15$	$y$

More the number of workers, faster will they build the wall.
So, the number of hours ($H$) and the number of workers ($W$) vary in inverse proportion.
$\Rightarrow H_1{W}_1=H_2{W}_2$

[1 mark]

$\Rightarrow 48\times 15=30\times y$
$\Rightarrow y=\frac{48\times 15}{30}=24$ workers

Hence, to finish the work in $30$ hours, $24$ workers are required.

[1 mark]