If a cylindrical piece of wood with a length of 20 decimeters is sawn into two pieces, the surface area increases by 8 square decimeters compared with the original one, what is the original volume of the wood in cubic decimeters?
一根长20分米的圆柱形木料，锯成两段后表面积比原来增加8平方分米，则木料原体积多少立方分米．
<gadget id="calculator">8 / 2</gadget>
<output>4</output>

<gadget id="calculator">4 * 20</gadget>
<output>80</output>

<result>80</result>