Two identical cylinders can be combined to form a cylinder with a height of 12 decimeters, but the surface area is reduced by 25.12 decimeters square. What is the volume of a cylinder.
两个完全一样的圆柱，能拼成一个高12分米的圆柱，但表面积减少了25.12平方分米．原来一个圆柱的体积是多少．
<gadget id="calculator">25.12 / 2</gadget>
<output>12.56</output>

<gadget id="calculator">12 / 2</gadget>
<output>6</output>

<gadget id="calculator">12.56 * 6</gadget>
<output>75.36</output>

<result>75.36</result>