After deducting 20% from a certain sum, and then 10% from the remainder, there is Rs. 7,200 left. Find the original sum.

Rs. 10,000

Let Initial Sum = 100x

Sum decreased by 20%

So remaining amount = 100x × \(\frac{4}{5}\) = 80x

Sum decreased by 10%

Amount left after 2nd deduction

So remaining amount = 80x × \(\frac{9}{10}\) = 72x

According to the question,

 72x = 7200

x = 100

100x = 10,000

So , initial Sum is 10,000