[ Arithmetic. Mental arithmetic, etc. ] $[\quad$ Motion problems $]$

Two buses were driving towards each other at constant speeds. The first one left Moscow at 11 AM and arrived in Yaroslavl at 4 PM, while the second one left Yaroslavl at 12 PM and arrived in Moscow at 5 PM. At what time did they meet?
Since each bus traveled exactly 5 hours, they cover the same distance of $S / 5$ per hour, where $S$ is the distance from Moscow to Yaroslavl. By the time the second bus departed, the first bus had already traveled $S / 5$. After that, each bus traveled a distance of $2 S / 5$ before meeting. Therefore, the buses met 2 hours after the second bus departed, which is at 14:00.

## Answer

At 14:00.