Xiao Ming went to swim in the swimming pool. He swam 4 back and forth in the swimming lane and swam a total of 400 meters. How long is the swimming lane in this swimming pool?
小明去游泳池游泳，他在泳道上游了4个来回，共游了400米，这个游泳池的泳道有多长？
<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<gadget id="calculator">400 / 8</gadget>
<output>50</output>

<result>50</result>