How many square decimeters of iron sheets are needed to make a cylindrical chimney with a bottom circumference of 25.12 decimeters and a length of 2 meters?
做5节底面周长为25.12分米，长2米的圆柱形烟囱，至少需要多少平方分米的铁皮？
<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<gadget id="calculator">25.12 * 20 * 5</gadget>
<output>2_512</output>

<result>2_512</result>