A train is 300 meters long. This train passes through a bridge with every branch of 900 meters, and it takes 3 minutes from the front of the train to the bridge to the end of the train leaving the bridge. How long is the bridge in meters?
一列火车长300米．这列火车通过一座大桥每分行900米，从车头开上桥到车尾离开桥共用3分．这座大桥全长多少米．
<gadget id="calculator">900 * 3</gadget>
<output>2_700</output>

<gadget id="calculator">2_700 - 300</gadget>
<output>2_400</output>

<result>2_400</result>