The radius of the bottom surface of a bucket without a lid is 3 decimeters, and the height is 5 decimeters. If such a pair of buckets are to be prepared, how much iron sheet should be prepared at least?
一个无盖水桶的底面半径是3分米，高是5分米，如果要做这样一对水桶至少准备多少铁皮？
<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">3.14 * 9</gadget>
<output>28.26</output>

<gadget id="calculator">3 * 2</gadget>
<output>6</output>

<gadget id="calculator">3.14 * 6 * 5</gadget>
<output>94.2</output>

<gadget id="calculator">28.26 + 94.2</gadget>
<output>122.46</output>

<gadget id="calculator">122.46 * 2</gadget>
<output>244.92</output>

<result>244.92</result>