Question

If 30 men can reap a field in 14 days, in how many days will 20 men reap it ?

Answer 1

The number of men doing a work and the number of days taken are in inverse proportion.

Let the number of days taken by $20$ men to reap the field be $a$.
Then, $30:20::$ inverse ratio of $14:a$

$=>30:20::a:14$
Applying the rule, product of extremes $=$ product of means

$30\times 14=20\times a$

$a=\frac{30\times 14}{20}$

$a=21$

Hence, $20$ men can reap the field in $21$ days.