A cylinder with a height of 4 decimeters is sawed vertically along the diameter of the bottom surface, and divided into two pieces on average. Their surface area is increased by 12 square decimeters compared with the original one. What is the diameter of the cylinder's bottom surface?
把一个高是4分米的圆柱体沿着底面直径垂直锯开，平均分成两块，它们的表面积比原来增加了12平方分米，圆柱的底面直径是多少．
<gadget id="calculator">12 / 2 / 4</gadget>
<output>3/2 = around 1.5</output>

<result>3/2 = around 1.5</result>