A water reservoir has a certain amount of water, and the river water flows into the reservoir evenly. 5 pumps can be drained continuously for 10 days; 6 identical pumps can be drained for 8 days. If it is required to be drained in 4 days, how many sets of the same water pumps are needed.
一水库存水量一定，河水均匀流入水库内．5台抽水机连续抽10天可以抽干；6台同样的抽水机连续抽8天可以抽干．若要求4天抽干，需要同样的抽水机多少台．
<gadget id="calculator">1 * 10 * 5</gadget>
<output>50</output>

<gadget id="calculator">1 * 6 * 8</gadget>
<output>48</output>

<gadget id="calculator">50 - 48</gadget>
<output>2</output>

<gadget id="calculator">10 - 8</gadget>
<output>2</output>

<gadget id="calculator">2 / 2</gadget>
<output>1</output>

<gadget id="calculator">10 * 1</gadget>
<output>10</output>

<gadget id="calculator">50 - 10</gadget>
<output>40</output>

<gadget id="calculator">40 / 4</gadget>
<output>10</output>

<gadget id="calculator">10 + 1</gadget>
<output>11</output>

<result>11</result>