Naughty participated in swimming class training during the summer vacation. He swam 2 back and forth in the swimming lane, and swam a total of 120 meters. How long is the swimming lane in this swimming pool?
淘气暑假参加游泳班训练，他在泳道内游了2个来回，共游了120米，这个游泳池的泳道有多长？
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">120 / 4</gadget>
<output>30</output>

<result>30</result>