To make a cylindrical tin bucket without a cover, the height is 30 cm, and the diameter of the bottom surface is 20 cm. How much iron is needed to make such a bucket?
做一个无盖的圆柱形铁皮水桶，高30厘米，底面直径20厘米，做这样一个水桶至少需要多少铁皮？
<gadget id="calculator">20 / 2</gadget>
<output>10</output>

<gadget id="calculator">10 ** 2</gadget>
<output>100</output>

<gadget id="calculator">3.14 * 100</gadget>
<output>314</output>

<gadget id="calculator">3.14 * 20 * 30</gadget>
<output>1_884</output>

<gadget id="calculator">314 + 1_884</gadget>
<output>2_198</output>

<result>2_198</result>