cuboid iron sheet ventilation pipe is 2 meters long, the cross section is a square, and the side length is 4dm. How many square meters of iron sheet are needed to make such a ventilation pipe?
一根长方体的铁皮通风管长2米，横截面是一个正方形，边长是4dm，做这样一根通风管至少要多少平方米铁皮．
<gadget id="calculator">4 / 10</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) * 4 * 2</gadget>
<output>16/5 = around 3.2</output>

<result>16/5 = around 3.2</result>