A train is 90 meters long. The train passes through the cave at a speed of 160 meters per minute. It takes 3 minutes. How long is the cave?
一列火车身长90米，火车以每分钟160米的速度通过山洞，用了3分钟，山洞长多少米．
<gadget id="calculator">160 * 3</gadget>
<output>480</output>

<gadget id="calculator">480 - 90</gadget>
<output>390</output>

<result>390</result>