Divide a circle with a radius of 4 decimeters into several parts along the radius, cut it and assemble it into an approximate rectangle. The perimeter of this rectangle is increased by how many decimeters compared with the perimeter of the original circle.
把一个半径为4分米的圆沿半径平均分成若干分，剪开后拼成一个近似的长方形，这个长方形的周长比原来圆的周长增加多少分米．
<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<result>8</result>