It takes 30 seconds for a train to pass through a 1200-meter bridge. It is known that the speed of the train is 50 m/s. How long is the train in meters?
一列火车通过1200米的大桥共用了30秒钟，已知火车的速度为50米/秒，这列火车长多少米？
<gadget id="calculator">50 * 30</gadget>
<output>1_500</output>

<gadget id="calculator">1_500 - 1_200</gadget>
<output>300</output>

<result>300</result>