In the supermarket, prices are reduced by 20%. What percentage more can you buy goods for the same salary?

1. Let’s denote the old price – P1, and the salary – S. At the old price it was possible to buy N1 goods: N1 = S / P1.

2. The price was reduced by 20%, and it became P2 = P1 – 20% * P1 = P1 – P1 * 20/100 = 0.8 * P1.

3. Now you can buy goods N2 = S / P2 = S / (0.8 * P1) = 1.25 * (S / P1) = 1.25 * N1.

4. We transform the expression for N2 through percentages:
N2 = 1.25 * N1 = N1 + 0.25 * N1 = N1 + N1 * 25/100 = N1 + 25% * N1.

Answer: After reducing the price of goods, you can buy 25% more.