Make 25 sections of cylindrical ventilation pipes with tin, each section is 1 meter long, and the diameter of the bottom circle is 0.2 meters, how many square meters of tin is needed?
用白铁皮制作圆柱形通风管25节，每节长1米，底面圆的直径是0.2米，问需要白铁皮多少平方米？
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