A cylindrical oil drum has a base radius of 4 decimeters and a height of 1 meter and 2 decimeters. How many square meters of iron sheet is needed to make this oil drum?
一个圆柱形的油桶，底面半径4分米，高1米2分米．制做这个油桶至少需要用铁皮多少平方米？
<gadget id="calculator">4 / 10</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) ** 2</gadget>
<output>4/25 = around 0.16</output>

<gadget id="calculator">3.14 * (4/25) * 2</gadget>
<output>1.0048</output>

<gadget id="calculator">3.14 * (2/5) * 2 * 1.2</gadget>
<output>3.0144</output>

<gadget id="calculator">1.0048 + 3.0144</gadget>
<output>4.0192</output>

<result>4.0192</result>