The train is 400 meters long, and it only takes 6 minutes to pass the bridge if it travels 100 meters per minute when passing a bridge (from the front of the train to the rear of the train leaving the bridge). Question: How long is the bridge in meters?
火车长400米，通过一座大桥(从车头上桥至车尾离开桥)每分钟行100米，则只需要6分钟即可通过大桥．问：大桥长多少米？
<gadget id="calculator">100 * 6</gadget>
<output>600</output>

<gadget id="calculator">600 - 400</gadget>
<output>200</output>

<result>200</result>