cuboid tin chimney, the bottom is a square with a side length of 40 cm and a height of 2 meters. What is the minimum square meter of iron sheets needed to make such a chimney
一长方体的铁皮烟囱，底面是边长为40厘米的正方形，高2米．做这样一个烟囱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</gadget>
<output>16/5 = around 3.2</output>

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