A chimney made of iron sheets is 3 meters long, 40 cm in diameter, and 3 cm in the welded area. How many square centimeters of iron sheets are needed to make this chimney?
一节用铁皮卷成的烟囱长3米，直径是40厘米，焊接的地方是3厘米，制造这节烟囱至少要铁皮多少平方厘米？
<gadget id="calculator">3.14 * 40</gadget>
<output>125.6</output>

<gadget id="calculator">125.6 + 3</gadget>
<output>128.6</output>

<gadget id="calculator">128.6 * 3 * 100</gadget>
<output>38_580</output>

<result>38_580</result>