Master Huang needs to make a 20-section ventilation pipe with a bottom diameter of 12 decimeters and a length of 30 decimeters. How much iron sheet is needed?
黄师傅要做20节底面直径是12分米，长是30分米的通风管，需要用多少铁皮？
<gadget id="calculator">3.14 * 12 * 30 * 20</gadget>
<output>22_608</output>

<result>22_608</result>