Expand the side of a cylinder to get a square with a side length of 12.56 decimeters. What is the radius of the base of this cylinder in decimeters?
将一个圆柱的侧面展开，得到一个边长为12.56分米的正方形，这个圆柱形的底面半径是多少分米．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<result>20</result>