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

Explanation

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.
$\Rightarrow M D = c o n s t a n t$
$\Rightarrow M_{1} D_{1} = M_{2} D_{2}$

[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.