## 30. Purchasing Power

While prices increased by $12 \%$, Mr. $X$'s salary increased by $22 \%$. By how much did his purchasing power increase?
30. Let's consider the previous salary of Monsieur $X$. Without its increase, his purchasing power would have decreased in the ratio $1 /(1+0.12)$. After the salary increase, his purchasing power increased by

$$
(1+0.22) /(1+0.12)=1.22 / 1.12 \approx 1.089 \text { times. }
$$

Therefore, his purchasing power increased by approximately $8.9 \%$.