Two circular iron pieces with a radius of 2 cm, one is fixed and the other rolls along the edge of the iron piece, the center of the rolling iron piece turns once and forms a circle, what is the radius of the formed circle in centimeters ?
两块半径都是2厘米的圆形铁片，一块固定不动，另一块沿着这块铁片的边缘滚动，滚动铁片的圆心转一周后形成一个圆，形成的圆的半径是多少厘米？
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<result>4</result>