Cut the largest circle out of a rectangle with a length of 10cm and a width of 8cm. How much does the area of this circle account for the area of the paper?
用一张长10cm、宽8cm的长方形剪一个最大的圆，这个圆的面积占这张纸面积的多少．
<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">4 ** 2</gadget>
<output>16</output>

<gadget id="calculator">10 * 8</gadget>
<output>80</output>

<gadget id="calculator">16 / 80</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">3.14 * (1/5)</gadget>
<output>0.628</output>

<result>0.628</result>