How many square meters of iron sheets are needed to make 20 sections of iron chimneys with a diameter of 12 cm and a height of 1.5 meters?
做20节直径是12厘米，高1.5米的铁皮烟囱，需要铁皮多少平方米？
<gadget id="calculator">12 / 100</gadget>
<output>3/25 = around 0.12</output>

<gadget id="calculator">3.14 * (3/25) * 1.5 * 20</gadget>
<output>11.304</output>

<result>11.304</result>