Question:
If 9 girls can prepare 135 garlands in 3 hours, how many girls are needed to prepare 270 garlands in 1 hour?
Solution:
Number of garlands made by 9 girls in 1 hour $=\frac{135}{3}=45$
Number of garlands made by 1 girl in 1 hour $=\frac{45}{9}=5$
$\therefore$ Number of girls required to make 270 garlands in 1 hour $=\frac{270}{5}=54$.