If the length of a rectangle is 7 cm and the width is 4 cm, what is its perimeter?
一个长方形的长是7厘米，宽是4厘米，它的周长是多少厘米？
<gadget id="calculator">7 + 4</gadget>
<output>11</output>

<gadget id="calculator">11 * 2</gadget>
<output>22</output>

<result>22</result>