A cylinder is cut into several equal parts along the diameter of its bottom surface, and assembled into an approximate cuboid. The surface area is increased by 80 square centimeters. What is its lateral area in square centimeters?
一个圆柱沿着它底面直径切成若干等份，拼成一个近似的长方体，表面积增加80平方厘米，它的侧面积为多少平方厘米．
<gadget id="calculator">80 / 2</gadget>
<output>40</output>

<gadget id="calculator">40 * 2 * 3.14</gadget>
<output>251.2</output>

<result>251.2</result>