Put an iron hoop on the outside of a circular bucket with a bottom radius of 20 cm, and the joint part is 0.4 decimeters. How long is the iron wire?
在一个底面半径为20厘米的圆形水桶外面打上一个铁箍，接头部分为0.4分米，需要用多长的铁丝？
<gadget id="calculator">20 / 10</gadget>
<output>2</output>

<gadget id="calculator">3.14 * 2 * 2</gadget>
<output>12.56</output>

<gadget id="calculator">12.56 + 0.4</gadget>
<output>12.96</output>

<result>12.96</result>