If a 28 cm long iron wire is used to form the largest square, what is the side length of this square?
用一根长28厘米的铁丝围成一个最大的正方形，这个正方形的边长是多少厘米？
<gadget id="calculator">28 / 4</gadget>
<output>7</output>

<result>7</result>