If three sections of round steel with a base radius of 2 cm are welded into a cylinder, the surface area will be reduced by how many square decimeters.
把3段底面半径为2厘米的圆钢焊接成一个圆柱体，表面积减少多少平方分米．
<gadget id="calculator">3.14 * 4 * 4</gadget>
<output>50.24</output>

<gadget id="calculator">50.24 / 100</gadget>
<output>0.5024</output>

<result>0.5024</result>