Wrap a copper wire around a small rod. When it is wound 50 times, the remaining copper coin is 21.2 cm. If it is wound 10 times, the copper coin is 10.2 cm short. How long is the copper wire in cm?
用铜线在一根小棒上绕圈，绕50圈时，测得铜钱余下21.2厘米，若再绕10圈，铜钱又差10.2厘米，这根铜线长度多少厘米？
<gadget id="calculator">21.2 + 10.2</gadget>
<output>31.4</output>

<gadget id="calculator">31.4 / 10</gadget>
<output>3.14</output>

<gadget id="calculator">3.14 * 50</gadget>
<output>157</output>

<gadget id="calculator">157 + 21.2</gadget>
<output>178.2</output>

<result>178.2</result>