To make 10 cylindrical ventilation pipes with a diameter of 20 cm and a length of 50 cm, how many square meters of iron sheet should be used at least?
制作10个直径20厘米、长50厘米的圆柱形通风管，至少要用多少平方米铁皮？
<gadget id="calculator">10 / 10_000</gadget>
<output>1/1_000 = around 0.001</output>

<gadget id="calculator">3.14 * 20 * 50 * (1/1_000)</gadget>
<output>3.14</output>

<result>3.14</result>