5. How has the purchasing power of the population changed? The product has become cheaper by $20 \%$. By what percentage can more of the product be bought for the same amount of money?
5. The product became cheaper by $20 \%$. Therefore, all the previously purchased goods could be bought by spending $80 \%$ of the money, and the remaining $20 \%$ could buy an additional $\frac{1}{4}$ of the goods, which constitutes $25 \%$.