A train is 720 meters long and travels 15 meters per second. It takes 64 seconds for the whole train to pass through a cave. How many meters is this cave?
一列火车长720米，每秒行驶15米，全车通过一个山洞用了64秒．这个山洞长多少米？
<gadget id="calculator">15 * 64</gadget>
<output>960</output>

<gadget id="calculator">960 - 720</gadget>
<output>240</output>

<result>240</result>