There is a rectangle with a length of 5 cm and a width of 4 cm, what is its perimeter in cm?
有一个长方形，长5厘米，宽4厘米，它的周长是多少厘米？
<gadget id="calculator">5 + 4</gadget>
<output>9</output>

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

<result>18</result>