Make 10 identical cylindrical ventilation pipes, the diameter of the bottom surface of the ventilation pipe is 20 cm, and the length is 1.2 meters. At least how many square meters of iron sheets are needed to make these ventilation pipes?
做10节相同的圆柱形通风管，通风管的底面直径是20厘米，长1.2米．做这些通风管至少需要多少平方米铁皮？
<gadget id="calculator">10 / 10_000</gadget>
<output>1/1_000 = around 0.001</output>

<gadget id="calculator">3.14 * 20 * 1.2 * 100 * (1/1_000)</gadget>
<output>7.536</output>

<result>7.536</result>