Two students, A and B, are running on the school's circular track. They run in opposite directions at the same place. A runs 52 meters per minute, and B runs 48 meters per minute. After 4 minutes, the two meet. How many meters is the school's circular track?
甲乙两位同学在学校环形跑道上跑步，两人在同一地点往相反方向跑，甲每分钟跑52米，乙每分钟跑48米，4分钟后两人相遇，学校环形跑道是多少米？
<gadget id="calculator">52 + 48</gadget>
<output>100</output>

<gadget id="calculator">100 * 4</gadget>
<output>400</output>

<result>400</result>