Cut the largest circle out of a square with a side length of 20 cm, what is the utilization rate of this square?
在一个边长为20厘米的正方形里剪一个最大的圆，这个正方形的利用率是多少？
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">20 * 20</gadget>
<output>400</output>

<gadget id="calculator">100 / 400</gadget>
<output>1/4 = around 0.25</output>

<gadget id="calculator">3.14 * (1/4)</gadget>
<output>0.785</output>

<result>0.785</result>