Master Wang cut the largest circle out of a rectangular iron sheet with a length of 8 decimeters and a width of 5 decimeters. What is the area of the remaining part?
王师傅在一块长8分米，宽5分米的长方形铁皮上剪下一个最大的圆，剩余部份的面积是多少平方分米？
<gadget id="calculator">8 * 5</gadget>
<output>40</output>

<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">(5/2) ** 2</gadget>
<output>25/4 = around 6.25</output>

<gadget id="calculator">3.14 * (25/4)</gadget>
<output>19.625</output>

<gadget id="calculator">40 - 19.625</gadget>
<output>20.375</output>

<result>20.375</result>