A cuboid chimney, each section of the chimney is 20 decimeters high, the bottom is 4 decimeters long and 3 decimeters wide, how many square meters of iron sheets are needed to make 12 such chimneys?
一种长方体烟囱，每节烟囱高20分米，底面长4分米，宽3分米，制作12节这样的烟囱，至少需要铁皮多少平方米？
<gadget id="calculator">20 / 10</gadget>
<output>2</output>

<gadget id="calculator">3 / 10</gadget>
<output>3/10 = around 0.3</output>

<gadget id="calculator">2 * (3/10)</gadget>
<output>3/5 = around 0.6</output>

<gadget id="calculator">4 / 10</gadget>
<output>2/5 = around 0.4</output>

<gadget id="calculator">(2/5) * 2</gadget>
<output>4/5 = around 0.8</output>

<gadget id="calculator">(3/5) + (4/5)</gadget>
<output>7/5 = around 1.4</output>

<gadget id="calculator">(7/5) * 2 * 12</gadget>
<output>168/5 = around 33.6</output>

<result>168/5 = around 33.6</result>