The inner diameter of the water pipe is 2 cm and the velocity of water in the pipe is 10 cm per second. A classmate went to the sink to wash his hands and forgot to turn off the tap when he left. How many liters of water are wasted in one class (40 minutes).
自来水管的内直径是2cm，水管内水的流速是每秒10cm．一位同学去水池洗手，走时忘记关掉水龙头．一节课(40分钟)浪费多少多少升水．
<gadget id="calculator">2 / 2</gadget>
<output>1</output>

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

<gadget id="calculator">1 * 1_000</gadget>
<output>1_000</output>

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

<gadget id="calculator">3.14 * 1 * 10 * 40 * (3/50)</gadget>
<output>75.36</output>

<result>75.36</result>