A cylindrical piece of wood is 4 decimeters long. After sawing it into two smaller cylinders, the surface area increases by 1.57 square decimeters. What is the original volume of the wood?
一根圆柱形木头长4分米，将它平均锯成2个小圆柱后，表面积增加1.57平方分米，原来木头的体积是多少．
<gadget id="calculator">1.57 / 2</gadget>
<output>0.785</output>

<gadget id="calculator">0.785 * 4</gadget>
<output>3.14</output>

<result>3.14</result>