A cylindrical steel is 3 meters long. After cutting it into 3 equal sections, the surface area increases by 20 square meters. What is the volume of this cylindrical steel in cubic meters?
一根圆柱形钢材长3米，把它切成相等的3段后，表面积增加了20平方米，那么这根圆柱形钢材的体积是多少立方米．
<gadget id="calculator">20 / 4</gadget>
<output>5</output>

<gadget id="calculator">5 * 3</gadget>
<output>15</output>

<result>15</result>