1. The older brother has $25 \%$ more money than the younger brother. What portion of his money should the older brother give to the younger brother so that they have an equal amount of money?
Answer: $1 / 10$ or $10 \%$.

Solution. Let the younger one have $x$ rubles. Then the older one has $1.25 x$ rubles. To make the amount of money equal, the older one should give the younger one $0.125 x$ rubles, which constitutes $10 \%$ of his money.

Evaluation. 10 points for the correct solution. If the solution states: "For example, let the younger one have 100 rubles. Then...", do not deduct points!