Peter could save 10% of his income. But two years later when his income is increased by 20%, he could save the same amount only as before. By how much percent has his expenditure increased ?

Correct Answer: $$22\frac{2}{9}\% $$
Let original income - Rs. 100
Then, saving = Rs. 10 and expenditure = Rs. 90
New income = Rs. 120
New saving = Rs. 10
New expenditure = Rs. (120 - 10) = Rs. 110
Increase in expenditure = Rs. (110 - 90) = Rs. 20
∴ Income % :
$$\eqalign{ & = \left( {\frac{{20}}{{90}} \times 100} \right)\% \cr & = 22\frac{2}{9}\% \cr} $$