A water pipe is used to fill an empty pool with a length of 7.2m, a width of 4.5m, and a depth of 1m. If the water pipe is filled with water at 810L per minute, how long will it take to fill the pool?
用水管向一个长7.2m、宽4.5m、深1m的空水池注水，如果水管每分钟注水810L，需要多长时间才能把水池注满？
<gadget id="calculator">1 / 0.81</gadget>
<output>1.234568</output>

<gadget id="calculator">7.2 * 4.5 * 1.234568</gadget>
<output>40.000003</output>

<result>40.000003</result>