A cuboid ventilation pipe is 2 meters long, and its cross-section is a square with a side length of 5 decimeters. How many square meters of iron sheet is needed to make such a ventilation pipe?
一个长方体通风管长2米，横截面为边长5分米的正方形，做这样一个通风管至少需要铁皮多少平方米？
<gadget id="calculator">5 / 10</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1/2) * 4 * 2</gadget>
<output>4</output>

<result>4</result>