If the outer diameter of the water pipe is 3 cm, the inner diameter is 2 cm, and the flow rate of water in the water pipe is 5 cm per second, how many liters of water will be wasted if the tap is not turned off during a class?
如果自来水管的外直径是3厘米，内直径是2厘米，水管内水的流速是每秒5厘米，那么一节课未关水笼头，要浪费多少升水？
<gadget id="calculator">2 / 2</gadget>
<output>1</output>

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

<gadget id="calculator">60 / 1_000</gadget>
<output>3/50 = around 0.06</output>

<gadget id="calculator">3.14 * 1 * 5 * 40 * (3/50)</gadget>
<output>37.68</output>

<result>37.68</result>