To make an uncovered cylindrical bucket with a base radius of 25 cm and a height of 50 cm, how many square centimeters of iron sheet are needed at least?
做一个没盖的圆柱形水桶，底面半径是25厘米，高50厘米，至少需要铁皮多少平方厘米？
<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>