A bridge is 3400 meters long. A train travels at a speed of 1200 meters per minute. It takes 3 minutes from the front of the train to the bridge and the rear of the train to leave the bridge. Find the length of the train?
一座桥长3400米，一辆火车以1200米/分的速度，从车头上桥到车尾离桥共用了3分钟，求火车的长度？
<gadget id="calculator">1_200 * 3</gadget>
<output>3_600</output>

<gadget id="calculator">3_600 - 3_400</gadget>
<output>200</output>

<result>200</result>