the ratio of income to the expenditure of a family is 9:4. find the income if the saving is ruppes 3600???

Since the ratio of income to the expenditure of a family is 9:4.
So, suppose the income and expenditure are 9x and 4x respectively.
Then saving amount = 9x - 4x = 5x
And the given saving amount is Rs.3600. so we have;
$$\begin{gathered} 5x = 3600 \\ \Rightarrow x = \frac{3600}{5} = 720 \end{gathered}$$
Therefore the income = $9\times 720$ = Rs.6480