rope with a length of 188.4 cm is wrapped around the trunk of a big tree exactly twice, and there is nothing left. What is the diameter of the big tree?
一根长188.4cm的绳子在一棵大树的树干上正好绕了2圈，没有剩余，这棵大树的直径是多少？
<gadget id="calculator">188.4 / 2 / 3.14</gadget>
<output>30</output>

<result>30</result>