The bottom of an oil drum is circular. The distance to roll this oil drum on the ground is 2.512 meters. What is the area of the bottom of this oil drum?
一个油桶的底面是圆形，把这个油桶放到在地面上滚动一圈的距离是2.512米，这个油桶的底面积是多少？
<gadget id="calculator">2.512 / 3.14 / 2</gadget>
<output>0.4</output>

<gadget id="calculator">0.4 ** 2</gadget>
<output>0.16</output>

<gadget id="calculator">3.14 * 0.16</gadget>
<output>0.5024</output>

<result>0.5024</result>