Question

If $9$ girls can prepare $135$ garlands in $3$ hours, how many girls are needed to prepare $270$ garlands in $1$ hour.

Answer 1

Given $135$ garlands in $3$ hours are prepared by $=9$ girls

$1$ garland in $3$ hours will be prepared by $=\frac{135}{9}=15$ girls

(Less work, less girls)

$1$ garland in $1$ hour will be prepare by $=\frac{15}{3}=5$ girls

(Less hour, more girls)
Therefore, $270$ garlands in $1$ hour will be prepared by $=\frac{270}{5}$ $=54$ girls.