To make a cylindrical tin bucket without a cover, the height is 5dm, and the radius of the bottom surface is 2dm, how many square decimeters of iron is needed at least?
做一个无盖的圆柱形铁皮水桶，高5dm，底面半径是2dm，至少需要铁皮多少平方分米？
<gadget id="calculator">2 * 2</gadget>
<output>4</output>

<gadget id="calculator">3.14 * 4 * 5</gadget>
<output>62.8</output>

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

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

<gadget id="calculator">62.8 + 12.56</gadget>
<output>75.36</output>

<result>75.36</result>