Water is poured into a container at a rate of 4 liters per minute. When there are 50 liters of water in the container, the pump starts to pump water out at a rate of 5 liters per minute. Q How many minutes is the minimum required to drain the container?
水按每分钟4升的速度注入一容器中．当容器中有50升水时，开始用泵按每分钟5升的速度向外抽水．问至少需要多少分钟将容器抽干？
<gadget id="calculator">5 - 4</gadget>
<output>1</output>

<gadget id="calculator">50 / 1</gadget>
<output>50</output>

<result>50</result>