If a cylinder is cut into two equal halves along the diameter of the base, the surface area increases by 40 square centimeters. What is the lateral area of the cylinder in square centimeters?
把一个圆柱沿底面直径切成相等的两半，表面积增加了40平方厘米，这个圆柱体的侧面积是多少平方厘米．
<gadget id="calculator">40 / 2</gadget>
<output>20</output>

<gadget id="calculator">3.14 * 20</gadget>
<output>62.8</output>

<result>62.8</result>