Fill a reservoir with a capacity of 600 cubic meters. (2/5) of this pool can be filled in 4 hours. If the pool is completely filled with water, how many hours will it take in total?
往一个容积为600立方米的蓄水池注水．4小时可以注满这个水池的(2/5)，如果要把这个水池全部注满水，一共需要几小时？
<gadget id="calculator">2 / 5</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) / 4</gadget>
<output>1/10 = around 0.1</output>

<gadget id="calculator">1 / (1/10)</gadget>
<output>10</output>

<result>10</result>