A cylindrical wooden barrel, measured from the inside, has a bottom radius of 2dm and a height of 5dm, what is the volume of this wooden barrel in dm**3.
一个圆柱形木桶，从里面量，底面半径是2dm，高是5dm，这个木桶的容积是多少dm**3．
<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4 * 5</gadget>
<output>62.8</output>

<result>62.8</result>