Uncle Wang is going to make a 10-meter cuboid chimney. The bottom of the chimney is a square with a side length of 5 decimeters. How many square meters of iron sheets are needed to make this chimney.
王叔叔准备做一根10米的长方体烟囱，烟囱底面是边长5分米的正方形，做这个烟囱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) * 10 * 4</gadget>
<output>20</output>

<result>20</result>