pool with an open outlet at the bottom. If 5 pumps are used to pump the water in 20 hours, if 8 pumps are used to pump the water in 15 hours. How many hours will it take to drain the water if only the water comes out from the water outlet?
水池，池底有一个打开的出水口．如果用5台抽水机20小时可将水抽完，如果用8台抽水机15小时可将水抽完．如果仅靠出水口出水，把水漏完需多少小时？
<gadget id="calculator">15 * 8</gadget>
<output>120</output>

<gadget id="calculator">8 * 15</gadget>
<output>120</output>

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

<gadget id="calculator">120 - 100</gadget>
<output>20</output>

<gadget id="calculator">20 - 15</gadget>
<output>5</output>

<gadget id="calculator">20 / 5</gadget>
<output>4</output>

<gadget id="calculator">15 * 4</gadget>
<output>60</output>

<gadget id="calculator">120 + 60</gadget>
<output>180</output>

<gadget id="calculator">180 / 4</gadget>
<output>45</output>

<result>45</result>