A cylindrical white tin ventilation pipe with a length of 4 meters and a nozzle diameter of 15 cm requires at least how many square meters of white tin.
一根长4米，管口直径15厘米的圆柱形白铁皮通风管，至少需要白铁皮多少平方米．
<gadget id="calculator">15 / 100</gadget>
<output>3/20 = around 0.15</output>

<gadget id="calculator">3.14 * (3/20) * 4</gadget>
<output>1.884</output>

<result>1.884</result>