A and B start from the same place at the same time and race around a circular track in the same direction. A runs 4 meters per second, and B runs 6 meters per second. After 4 minutes, B catches up with A and asks how long the track is in meters ?
甲、乙两人同时从同一地点出发，同向绕一环形跑道赛跑，甲每秒跑4米，乙每秒跑6米，过了4分钟，乙追上了甲，问跑道一周长多少米？
<gadget id="calculator">6 - 4</gadget>
<output>2</output>

<gadget id="calculator">2 * 240</gadget>
<output>480</output>

<result>480</result>