There are two steel pipes with a radius of 5 cm, which need to be tied with iron wires. If two steel pipes are to be tied, how many meters of iron wire should be used at least?
有2根半径都是5厘米的钢管，要用铁丝捆起来，如果要捆两道，那么至少要用多少米的铁丝？
<gadget id="calculator">3.14 * 2 * 5</gadget>
<output>31.4</output>

<gadget id="calculator">5 * 2 * 2</gadget>
<output>20</output>

<gadget id="calculator">31.4 + 20</gadget>
<output>51.4</output>

<result>51.4</result>