A section of cylindrical iron sheet ventilation pipe is 15dm long, and the radius of the nozzle is 2dm. How much dm**2 iron sheets are needed to make such a section of ventilation pipe.
一节圆柱形铁皮通风管长15dm，管口半径2dm，制成一节这样的通风管需多少dm**2的铁皮．
<gadget id="calculator">2 * 3.14 * 2 * 15</gadget>
<output>188.4</output>

<result>188.4</result>