Make 10 sections of ventilation pipes with iron sheets, each section is 80 cm long, and the diameter of the bottom circle is 10 cm. How many square meters of iron sheet is needed at least?
用铁皮做通风管10节，每节长80厘米，底面圆的直径是10厘米．至少需要铁皮多少平方米？
<gadget id="calculator">3.14 * 10 * 80</gadget>
<output>2_512</output>

<gadget id="calculator">10 / 10_000</gadget>
<output>1/1_000 = around 0.001</output>

<gadget id="calculator">2_512 * (1/1_000)</gadget>
<output>314/125 = around 2.512</output>

<result>314/125 = around 2.512</result>