To make a cylindrical chimney with a height of 4 meters and a bottom circumference of 1.25 meters, how many square meters of iron sheet is needed.
做一个高4米，底周长1.25米的圆柱形烟囱，需要铁皮多少平方米．
<gadget id="calculator">1.25 * 4</gadget>
<output>5</output>

<result>5</result>