If a 20dm long cylindrical stick is sawed into two pieces, the surface area increases by 4dm**2, what is the original volume of the stick in dm**3.
把20dm长的圆柱形木棒锯成两段，表面积增加了4dm**2，原来木棒的体积是多少dm**3．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">2 * 1 * 20</gadget>
<output>40</output>

<result>40</result>