wire surrounds a rectangle with a length of 15 cm and a width of 3 cm. If the wire is surrounded by a square, what is the side length of the square?
一根铁丝围成一个长方形，长是15厘米，宽是3厘米．如果把这根铁丝围成一个正方形，正方形的边长是多少厘米？
<gadget id="calculator">15 + 3</gadget>
<output>18</output>

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

<gadget id="calculator">18 * (1/2)</gadget>
<output>9</output>

<result>9</result>