To make a chimney with a length of 5 meters, its cross-section is a square with a side length of 2 decimeters, how many square meters of iron sheet should be used at least.
做一根长5米的烟囱，它的横截面是边长2分米的正方形，至少要用多少平方米铁皮．
<gadget id="calculator">2 / 10</gadget>
<output>1/5 = around 0.2</output>

<gadget id="calculator">(1/5) * 5 * 4</gadget>
<output>4</output>

<result>4</result>