To make a cylindrical tin oil drum (with a cover), the radius of the bottom surface is 3 decimeters, and the height is 5 decimeters. How many square decimeters of iron skin should be used at least?
做一个圆柱形铁皮油桶(有盖)，底面半径是3分米，高5分米，至少要用多少平方分米的铁皮？
<gadget id="calculator">3.14 * 3 * 2 * 5</gadget>
<output>94.2</output>

<gadget id="calculator">3 ** 2</gadget>
<output>9</output>

<gadget id="calculator">3.14 * 9 * 2</gadget>
<output>56.52</output>

<gadget id="calculator">94.2 + 56.52</gadget>
<output>150.72</output>

<result>150.72</result>