To make a cylindrical tin bucket without a cover, the radius of the bottom surface is 25 cm, and the height is 50 cm. How many square centimeters of iron skin is needed to make such a bucket?
做一个无盖的圆柱体铁皮水桶，底面半径是25厘米，高是50厘米，做一只这样的水桶大约需要多少平方厘米的铁皮？
<gadget id="calculator">25 ** 2</gadget>
<output>625</output>

<gadget id="calculator">3.14 * 625</gadget>
<output>1_962.5</output>

<gadget id="calculator">3.14 * 25 * 2 * 50</gadget>
<output>7_850</output>

<gadget id="calculator">1_962.5 + 7_850</gadget>
<output>9_812.5</output>

<result>9_812.5</result>