A ventilation pipe is 20 meters long, the mouth of the pipe is a square, and the side length is 0.5 meters. How many square meters of iron sheets are needed to make 3 such ventilation pipes?
一个通风管道长20米，管口是一个正方形，边长0.5米，做3个这样的通风管需要铁皮多少平方米？
<gadget id="calculator">0.5 * 0.5 * 20 * 3</gadget>
<output>15</output>

<result>15</result>