Make a ventilation pipe with a length of 4 meters with white iron sheet, and the diameter of the nozzle is 15 cm. How many square meters of white iron sheet should be used at least to make this ventilation pipe?
用白铁皮做一根长4米的通风管，管口的直径是15厘米，做这个通风管至少要用白铁皮多少平方米？
<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>