If two squares with side length 3cm are put together to form a rectangle, what is the perimeter of the rectangle in centimeters?
两个边长是3cm的正方形，拼成一个长方形，长方形的周长是多少厘米
<gadget id="calculator">3 + 3 + 3</gadget>
<output>9</output>

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

<result>18</result>