If the length of a rectangle is 6 cm and the width is 4 cm, what is the perimeter of the rectangle in cm?
一个长方形的长是6厘米，宽是4厘米，这个长方形的周长是多少厘米．
<gadget id="calculator">6 + 4</gadget>
<output>10</output>

<gadget id="calculator">10 * 2</gadget>
<output>20</output>

<result>20</result>