A semicircular artificial lake has a measured diameter of 80m. How many meters does it take to walk around the lake?
一个半圆形的人工湖，量得直径是80m，沿湖走一圈需要走多少米？
<gadget id="calculator">80 / 2</gadget>
<output>40</output>

<gadget id="calculator">3.14 * 40</gadget>
<output>125.6</output>

<gadget id="calculator">125.6 + 80</gadget>
<output>205.6</output>

<result>205.6</result>