If two squares with an area of 81 square centimeters are put together to form a rectangle, what is the perimeter of the rectangle in centimeters?
把两个面积各是81平方厘米的正方形拼成一个长方形，这个长方形的周长是多少厘米．
<gadget id="calculator">9 + 9</gadget>
<output>18</output>

<gadget id="calculator">18 + 9</gadget>
<output>27</output>

<gadget id="calculator">27 * 2</gadget>
<output>54</output>

<result>54</result>