A cylindrical gasoline barrel has a bottom diameter of 10 decimeters and a height of 20 decimeters. How many square decimeters of iron sheet is needed to make such a gasoline barrel?
一个圆柱的汽油桶，底面直径是10分米，高是20分米，做这样一个汽油桶需要铁皮多少平方分米？
<gadget id="calculator">3.14 * 10 * 20</gadget>
<output>628</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 * 2</gadget>
<output>25.12</output>

<gadget id="calculator">628 + 25.12</gadget>
<output>653.12</output>

<result>653.12</result>