A circular runway is 400 meters long. A rides a bicycle at 450 meters per minute, and B runs at 250 meters per minute. The two start off at the same time at the same time. How many minutes do they meet?
一条环形跑道长400米，甲骑自行车每分钟450米，乙跑步每分钟250米，两人同时同地同向出发，经过多少分钟两人相遇？
<gadget id="calculator">450 - 250</gadget>
<output>200</output>

<gadget id="calculator">400 / 200</gadget>
<output>2</output>

<result>2</result>