A semi-circular arched chicken pen is surrounded by a fence of 25.12 meters along one side of a straight wall. What is the radius of the chicken circle in meters?
沿一条直围墙的一侧用25.12米的篱笆围了一个半圆拱形的鸡圈，这个鸡圈的半径是多少米？
<gadget id="calculator">25.12 * 2</gadget>
<output>50.24</output>

<gadget id="calculator">50.24 / 3.14 / 2</gadget>
<output>8</output>

<result>8</result>