train crosses a bridge at a speed of 900m per minute. It takes 3 minutes from the front of the train on the bridge to the end of the train leaving the bridge. It is known that the length of the train is 300m. How long is the bridge?
一列火车以每分钟900m的速度过一座桥，从车头开始上桥到车尾离开桥共需要3分钟，已知火车的车身长为300m，这座桥有多长？
<gadget id="calculator">3 * 900</gadget>
<output>2_700</output>

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

<result>2_400</result>