To make 5 ventilation pipes with a length of 2 meters and a diameter of 0.2 meters, at least how many square meters of iron sheets are needed.
做5根长2米，管口直径是0.2米的通风管，至少需要铁皮多少平方米．
<gadget id="calculator">3.14 * 0.2 * 2 * 5</gadget>
<output>6.28</output>

<result>6.28</result>