Make 10 cylindrical ventilation pipes with iron sheets, each section is 100 cm long, and the radius of the bottom circle is 5 cm. At least how many square centimeters of iron sheets are needed.
用铁皮制作10节圆柱形通风管，每节长100厘米，底面圆的半径是5厘米．至少需要用铁皮多少平方厘米．
<gadget id="calculator">3.14 * 5 * 2 * 100 * 10</gadget>
<output>31_400</output>

<result>31_400</result>