Question

If 15 men can do a work in 12 days, how many men will do the same work in 6 days?
[2 marks]

Answer 1

Let the required number of men be $x$.

Number of men	$15$	$x$
Number of days	$12$	$6$

As number of men [M] will increase, the number of days [D] to finish a work will be less.
Hence, it is a case of inverse proportion.
$\Rightarrow MD=constant$
$\Rightarrow M_1{D}_1=M_2{D}_2$

[1 mark]

$\Rightarrow 15\times 12=x\times 6$
$\Rightarrow x=\frac{15\times 12}{6}=30$

Therefore, the required number of men to finish the work in 30 days is $30$ men.

[1 mark]