If a radius is shortened to the original (1/4), then the area is reduced to the original
一个半径缩短为原来的(1/4)，那么面积缩小为原来的多少
<gadget id="calculator">1 / 16</gadget>
<output>1/16 = around 0.0625</output>

<result>1/16 = around 0.0625</result>