Question:
If 36 men can do a piece of work in 25 days, in how many days will 15 men do it?
Solution:
Let x be the number of days in which 15 men can do a piece of work.
Since the number of men hired and the number of days taken to do a piece of work are in inverse variation, we have:
$36 \times 25=x \times 15$
$\Rightarrow x=\frac{36 \times 25}{15}$
$=\frac{900}{15}$
$=60$
Thus, the required number of days is 60 .