To make a tin chimney with a length of 0.5 meters, a width of 0.5 meters and a height of 10 meters, how many meters of tin is needed at least**2.
做一根长0.5米，宽0.5米，高10米的铁皮烟囱，至少需要铁皮多少米**2．
<gadget id="calculator">0.5 * 10 * 4</gadget>
<output>20</output>

<result>20</result>