square iron sheet has a circumference of 20 decimeters, and the largest circle is to be cut out. What is the diameter of this circle in decimeters?
一块正方形铁皮，周长是20分米，要剪下一个最大的圆，这个圆的直径是多少分米．
<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<result>5</result>