Cut a cylinder along the radius of the bottom surface, divide it into several parts on average, put them together to form an approximate cuboid, and increase the surface area by 40 square centimeters, then what is the side area of the cylinder in square centimeters?
把一个圆柱沿底面半径切开，平均分成若干份，拼成一个近似的长方体，表面积增加40平方厘米，那么这个圆柱的侧面积是多少平方厘米．
<gadget id="calculator">3.14 * 2 * 20</gadget>
<output>125.6</output>

<result>125.6</result>