A square iron sheet has a circumference of 100 cm, and the largest circle is to be cut out. What is the radius of this circle in cm?
一个正方形的铁皮，周长是100cm，要剪下一个最大的圆，这个圆的半径是多少cm．
<gadget id="calculator">100 / 4</gadget>
<output>25</output>

<gadget id="calculator">25 / 2</gadget>
<output>25/2 = around 12.5</output>

<result>25/2 = around 12.5</result>