A train is 200 meters long, and it passes through a 200-meter-long tunnel at a speed of 10 meters per second. How many seconds does it take from the front of the train entering the tunnel to the end of the train leaving the tunnel?
一列火车长200米，它以每秒10米的速度穿过200米长的隧道，从车头进入隧道到车尾离开隧道共需要多少秒？
<gadget id="calculator">200 + 200</gadget>
<output>400</output>

<gadget id="calculator">400 / 10</gadget>
<output>40</output>

<result>40</result>