If a cylinder whose base diameter is 4 decimeters is cut into two small cylinders, how much dm**2 will the surface area increase?
把一段底面直径是4分米的圆柱体截成两个小圆柱体，则表面积增加了多少dm**2．
<gadget id="calculator">4 / 2</gadget>
<output>2</output>

<gadget id="calculator">2 ** 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4 * 2</gadget>
<output>25.12</output>

<result>25.12</result>