steamboat is sailing on a river, and the engine is always running in the same state. At this time, it takes 3 hours to sail along the current, and 4 hours to sail against the current. If an empty barrel drifts along the river, how long does it take to cover the same distance?
一只汽船在一条河上航行，发动机总是以同一状态运转，这时它顺水航行需要3小时，逆水航行需要4小时，请问如果一只空桶顺水漂移，走完同样长的路程需要多少时间？
<gadget id="calculator">1 / 3</gadget>
<output>1/3 = around 0.333333</output>

<gadget id="calculator">1 / 4</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">(1/3) - (1/4)</gadget>
<output>1/12 = around 0.083333</output>

<gadget id="calculator">(1/12) / 2</gadget>
<output>1/24 = around 0.041667</output>

<gadget id="calculator">1 / (1/24)</gadget>
<output>24</output>

<result>24</result>