A 2-meter-long ventilation pipe has a cross-section of a square with a side length of 2 decimeters. How many square decimeters of iron sheet are needed to make this ventilation pipe?
一根2米长的通风管，横截面是边长2分米的正方形，制作这个通风管至少需要铁皮多少平方分米？
<gadget id="calculator">2 * 10</gadget>
<output>20</output>

<gadget id="calculator">2 * 4 * 20</gadget>
<output>160</output>

<result>160</result>