A cylindrical iron chimney has a bottom diameter of 30 cm and a length of 40 cm. How many square centimeters of iron sheets are needed to make this chimney?
一个圆柱形铁皮烟囱，底面直径30厘米，长40厘米，做这个烟囱至少需要多少平方厘米的铁片．
<gadget id="calculator">3.14 * 30 * 40</gadget>
<output>3_768</output>

<result>3_768</result>