The cross-section of a ventilation pipe is a square with a side length of 0.5 meters and a length of 2.5 meters. If 100 such ventilation pipes are made of iron sheets, how many square meters of iron sheets are needed?
一个通风管的横截面是边长是0.5米的正方形，长2.5米，如果用铁皮做这样的通风管100只，需要多少平方米的铁皮？
<gadget id="calculator">0.5 * 4 * 2.5 * 100</gadget>
<output>500</output>

<result>500</result>