To make 10 ventilation pipes with a square mouth, a side length of 40 cm, and a pipe length of 2 meters, how many square meters of iron sheet are needed at least?
做一个管口是正方形，边长为40厘米，管长是2米的通风管10根，至少需要铁皮多少平方米？
<gadget id="calculator">40 / 100</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) * 4 * 2 * 10</gadget>
<output>32</output>

<result>32</result>