A circle is surrounded by a piece of iron wire with a radius of exactly 5dm. If a square is surrounded by this wire, what is the side length of the square in dm?
用一根铁丝围成一个圆，半径正好是5dm．如果用这根铁丝围成一个正方形，正方形的边长是多少dm．
<gadget id="calculator">5 / 4</gadget>
<output>5/4 = around 1.25</output>

<gadget id="calculator">2 * 3.14 * (5/4)</gadget>
<output>7.85</output>

<result>7.85</result>