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?

Let original incorne + $₹$ 100. Then, saving =$=₹10$ and expenditure= $₹$90. New income=$₹$ 120. 

New saving=? I 0. 

Now expenditure =$₹$(120- 10) = f 110. Increase in expenditure=$₹$ (110-90)=$₹$ 20

$\therefore$ Increase % $=\left(\frac{20}{90}\times 100\right)\mathrm{\%}=22\frac{2}{9}\mathrm{\%}$