A square log is 20 decimeters long. After sawing it into two pieces, the surface area increases by 5 decimeters. What is the volume of this square log in cubic decimeters?
一根方木长20分米，把它锯成两段后，表面积增加了5平方分米，这根方木的体积是多少立方分米．
<gadget id="calculator">5 / 2</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">(5/2) * 20</gadget>
<output>50</output>

<result>50</result>