Cut the largest circle out of a rectangular cardboard with a length of 8 cm and a width of 5 cm. What is the area of the circle in square decimeters?
在一个长8厘米、宽5厘米的长方形纸板上剪一个最大的圆，圆的面积是多少平方分米．
<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">(25/4) / 100</gadget>
<output>1/16 = around 0.0625</output>

<gadget id="calculator">3.14 * (1/16)</gadget>
<output>0.19625</output>

<result>0.19625</result>