A train is 120 meters long, and it takes 20 seconds for the entire train to pass through a 480-meter railway bridge. How many meters per second does the train travel on average?
一列火车长120米，全车通过480米的铁路桥需要20秒，这列火车平均每秒行多少米？
<gadget id="calculator">120 + 480</gadget>
<output>600</output>

<gadget id="calculator">600 / 20</gadget>
<output>30</output>

<result>30</result>