How many meters of iron wire are needed to tie up 4 logs with a cross-sectional diameter of 3 decimeters with iron wire (the joints are ignored).
把横截面直径是3分米的4根圆木用铁丝捆起来(接头忽略不记)至少需要多少米长的铁丝．
<gadget id="calculator">9.42 + 12</gadget>
<output>21.42</output>

<gadget id="calculator">21.42 / 10</gadget>
<output>2.142</output>

<result>2.142</result>