Xiaohong and Xiaoming are running on the circular track. They start from the same place and walk with their backs. Xiaohong runs 4 meters per second, Xiao Ming runs 6 meters per second, and they meet each other in 25 seconds. How long is the circular track?
小红和小明在环形跑道上跑步，两人从同一地点出发，背向而行．小红每秒跑4米，小明每秒跑6米，25秒两人相遇，这个环形跑道长多少？
<gadget id="calculator">4 + 6</gadget>
<output>10</output>

<gadget id="calculator">10 * 25</gadget>
<output>250</output>

<result>250</result>