The cross-section of a ventilation pipe is a square with side length 4dm and length 3m. If iron sheets are used to make such a ventilation pipe with 80 knots, how much area of iron sheet is needed?
一节通风管的横截面是边长4dm的正方形，长3m．如果用铁皮做这样的通风管80节，需要多大面积的铁皮？
<gadget id="calculator">4 / 10</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) * 4 * 3 * 80</gadget>
<output>384</output>

<result>384</result>