To process a cuboid iron sheet oil barrel, which is 2.5 decimeters in length, 1.6 decimeters in width, and 3 decimeters in height, how many square decimeters of iron sheet should be used at least?
加工一个长方体铁皮油桶，长2.5分米，宽1.6分米，高3分米，至少要用多少平方分米铁皮？
<gadget id="calculator">2.5 * 1.6</gadget>
<output>4</output>

<gadget id="calculator">2.5 * 3</gadget>
<output>7.5</output>

<gadget id="calculator">1.6 * 3</gadget>
<output>4.8</output>

<gadget id="calculator">4 + 7.5 + 4.8</gadget>
<output>16.3</output>

<gadget id="calculator">16.3 * 2</gadget>
<output>32.6</output>

<result>32.6</result>