To make a cylindrical tin bucket without a cover, the diameter of the bottom surface is 40 cm, and the height is 5 decimeters. How many square decimeters of iron is needed to make this bucket?
做一个无盖的圆柱形铁皮水桶，底面直径是40厘米，高是5分米，制作这个水桶至少需要铁皮多少平方分米？
<gadget id="calculator">40 / 10</gadget>
<output>4</output>

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

<gadget id="calculator">40 / 10 / 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">62.8 + 12.56</gadget>
<output>75.36</output>

<result>75.36</result>