To make a cylindrical bucket without a cover, the diameter of the bottom surface is 4 decimeters, and the height is 5.5 decimeters. How many square decimeters of iron sheet are needed at least?
做一个无盖的圆柱形水桶，底面直径是4分米，高是5.5分米，至少需要铁皮多少平方分米？
<gadget id="calculator">3.14 * 4 * 5.5</gadget>
<output>69.08</output>

<gadget id="calculator">4 / 2</gadget>
<output>2</output>

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

<gadget id="calculator">3.14 * 4</gadget>
<output>12.56</output>

<gadget id="calculator">69.08 + 12.56</gadget>
<output>81.64</output>

<result>81.64</result>