train passes through a 1,720-meter cave at a speed of 50 m/s. It takes 38 seconds. How long is the train?
一列火车以50米/秒的速度通过一个1720米的山洞，用了38秒，火车长多少米？
<gadget id="calculator">50 * 38</gadget>
<output>1_900</output>

<gadget id="calculator">1_900 - 1_720</gadget>
<output>180</output>

<result>180</result>