Divide a circle with a radius of 2dm into several parts on average, cut it and put it together to form an approximate rectangle. How much dm does the perimeter of the rectangle increase compared to the perimeter of the circle?
把一个半径是2dm的圆平均分成若干份，剪开后拼成一个近似的长方形，这个长方形的周长比圆周长增加了多少dm．
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<result>4</result>