To make a 5-section bottom diameter of 2 decimeters and a cylindrical ventilation pipe with a length of 8 decimeters, how much iron sheet is needed at least?
做5节底面直径是2分米，长8分米的圆柱形通风管，至少需要多少铁皮？
<gadget id="calculator">3.14 * 2 * 8 * 5</gadget>
<output>251.2</output>

<result>251.2</result>