A cylinder is expanded to form a square. The diameter of the base of the cylinder is 4 decimeters. What is its height in decimeters?
一个圆柱体侧面展开得到一个正方形，这个圆柱的底面直径是4分米，它的高是多少分米．
<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<result>12.56</result>