Question

A man spends $78$% of his monthly income and saves $Rs.1,100$. What is his monthly income?

Answer 1

Let his monthly income be $Rs.100$. Then his expenditure is $Rs.78$. Therefore, his savings is $100-78=Rs.22$.
Let us put this in reverse way. If the saving is $Rs.22$, then the income is $Rs.100$. Hence if the savings is $Rs.1$, then the income is $Rs\frac{100}{22}$.
If the savings is $Rs.1,100$, then the income is $\frac{100}{22}\times 1100=5,000$ rupees.
Hence his monthly income is $Rs.5,000$.