Three pieces of wood with the same diameter of 10 cm are tied into a bundle with rope. If you tie 3 loops, how long is the rope? (connectors not counted)
把三根同样为直径10厘米的木头，用绳子捆成一捆．如果绑3圈，需要多长的绳子？(接头不计)
<gadget id="calculator">3.14 * 10</gadget>
<output>31.4</output>

<gadget id="calculator">10 * 4</gadget>
<output>40</output>

<gadget id="calculator">31.4 + 40</gadget>
<output>71.4</output>

<gadget id="calculator">71.4 * 3</gadget>
<output>214.2</output>

<result>214.2</result>