To make a chimney with a length and width of 4 decimeters and a height of 1 meter, at least how many square meters of iron sheets are needed.
做一个长和宽都是4分米、高1米的烟囱，至少需要多少平方米的铁皮．
<gadget id="calculator">4 * 1 * 10</gadget>
<output>40</output>

<gadget id="calculator">40 + 40</gadget>
<output>80</output>

<gadget id="calculator">2 / 100</gadget>
<output>1/50 = around 0.02</output>

<gadget id="calculator">80 * (1/50)</gadget>
<output>8/5 = around 1.6</output>

<result>8/5 = around 1.6</result>