A cylindrical water pipe with an inner diameter of 20 cm and a flow rate of water in the pipe is 3 decimeters per second, how many liters of water flow through it per second.
一个圆柱形水管，管内直径是20厘米，水在管内的流速是每秒3分米，每秒流过的水是多少升．
<gadget id="calculator">20 / 10</gadget>
<output>2</output>

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

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

<gadget id="calculator">3.14 * 1 * 3</gadget>
<output>9.42</output>

<result>9.42</result>