train is 360 meters long and travels 15 meters per second. It takes 40 seconds for the whole train to pass through a cave. How long is the cave in meters?
一列火车长360米，每秒钟行15米，全车通过一个山洞需40秒，这个山洞长多少米．
<gadget id="calculator">15 * 40</gadget>
<output>600</output>

<gadget id="calculator">600 - 360</gadget>
<output>240</output>

<result>240</result>