Xiao Ming surrounded a rectangle with a length of 15cm and a width of 9cm with a piece of iron wire. If it is changed into a square, what is the side length of the square in centimeters?
小明用一根铁丝围了一个长15cm，宽9cm的长方形，如果改成正方形，这个正方形的边长是多少厘米？
<gadget id="calculator">15 + 9</gadget>
<output>24</output>

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

<gadget id="calculator">24 * (1/2)</gadget>
<output>12</output>

<result>12</result>