There is a well that continuously flows out spring water, and the amount of spring water flowing out of the spring is the same every hour. If 8 pumps are used to pump the water from this well, it can be pumped in 12 minutes; if 3 pumps are used, it can be pumped in 36 minutes; the water is limited to 20 minutes. How many pumps are needed.
有一口不断流出泉水的井，每小时流出泉水量相同，这口井的水如果用8台抽水机，12分钟可以抽完；如果用3台抽水机，36分钟可以抽完；问限定在20分钟抽完，需要多少台抽水机．
<gadget id="calculator">12 * 8</gadget>
<output>96</output>

<gadget id="calculator">36 * 3</gadget>
<output>108</output>

<gadget id="calculator">108 - 96</gadget>
<output>12</output>

<gadget id="calculator">36 - 12</gadget>
<output>24</output>

<gadget id="calculator">12 / 24</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) * 12</gadget>
<output>6</output>

<gadget id="calculator">96 - 6</gadget>
<output>90</output>

<gadget id="calculator">20 * (1/2)</gadget>
<output>10</output>

<gadget id="calculator">90 + 10</gadget>
<output>100</output>

<gadget id="calculator">100 / 20</gadget>
<output>5</output>

<result>5</result>