Cut a cylindrical wood with a height of 20 cm into two identical half cylinders vertically along the diameter of the bottom surface, and increase the surface area by 520 square centimeters. Calculate the lateral area of the original cylindrical wood.
把一个高20cm的圆柱形木头沿底面直径垂直切成两个相同的半圆柱体，表面积增加520平方厘米，求原来这个圆柱形木头的侧面积．
<gadget id="calculator">520 / 2</gadget>
<output>260</output>

<result>260</result>