A cylindrical oil barrel has a base radius of 20 cm measured from the inside and a height of 3 decimeters. What is the volume of this oil barrel?
一个圆柱形油桶，从里面量的底面半径是20厘米，高是3分米．这个油桶的容积是多少？
<gadget id="calculator">20 / 10</gadget>
<output>2</output>

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4 * 3</gadget>
<output>37.68</output>

<result>37.68</result>