A cylindrical bucket without a lid has a bottom diameter of 20 cm and a height of 30 cm. How much iron sheet is needed to make such a pair of buckets?
一个无盖的圆柱形水桶，底面直径为20厘米，高为30厘米，制作这样一对水桶，至少要多少铁皮？
<gadget id="calculator">3.14 * 20 * 30</gadget>
<output>1_884</output>

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

<gadget id="calculator">2_198 * 2</gadget>
<output>4_396</output>

<result>4_396</result>