Question:
A man saves 18% of his monthly income. If he saves Rs 3780 per month, what is his monthly income?
Solution:
Let Rs $x$ be his monthly income.
His savings $=18 \%$ of Rs $\mathrm{x}$
$=\operatorname{Rs}\left(x \times \frac{18}{100}\right)$
$=\operatorname{Rs} \frac{9 x}{50}$
Now, $\frac{9 x}{50}=3780$
$\Rightarrow x=\mathrm{Rs}\left(3780 \times \frac{50}{9}\right)$
$\Rightarrow x=\mathrm{Rs} 21000$
$\therefore$ His monthly income is Rs. 21000 .