It takes 6.5 seconds for a train to pass a road sign, and 23 seconds to pass a 300-meter-long bridge. How many seconds does it take to pass through a 800-meter-long cave?
一列火车经过一路标用6.5秒，通过一座长300米的桥用了23秒，它经过长800米的山洞多少秒．
<gadget id="calculator">23 - 6.5</gadget>
<output>16.5</output>

<gadget id="calculator">300 / 16.5</gadget>
<output>18.181818</output>

<gadget id="calculator">800 / 18.181818</gadget>
<output>44</output>

<gadget id="calculator">44 + 6.5</gadget>
<output>50.5</output>

<result>50.5</result>