A cuboid of wood is 3 meters long, cut twice along the direction parallel to the cross section, the surface area increases by 20 square decimeters, what is the volume of the original cuboid in cubic decimeters?
一个长方体木料长3米，沿与横截面平行的方向截2次，表面积增加20平方分米，求原来长方体的体积是多少立方分米．
<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<gadget id="calculator">3 * 10</gadget>
<output>30</output>

<gadget id="calculator">5 * 30</gadget>
<output>150</output>

<result>150</result>