How many square centimeters of iron sheets are needed to make 8 cylindrical ventilating pipes of the same size with each section having a diameter of 20 cm and a length of 40 cm? (Joints are not counted).
用铁皮做8节同样大小的圆柱形通风管，每节的直径是20厘米，长40厘米，一共需要多少平方厘米的铁皮？(接头处不计)．
<gadget id="calculator">3.14 * 20 * 40 * 8</gadget>
<output>20_096</output>

<result>20_096</result>