There is a rectangle surrounded by iron wire, the length is 25 cm, and the width is 17 cm. If it is changed into a square, what is the side length of the square?
有一个用铁丝围成的长方形，长25厘米，宽17厘米，如果把它改围成一个正方形，围成的正方形边长是多少厘米？
<gadget id="calculator">25 + 17</gadget>
<output>42</output>

<gadget id="calculator">2 / 4</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">42 * (1/2)</gadget>
<output>21</output>

<result>21</result>