The length of the rectangle is 15 cm, the width is 8 cm, what is the perimeter in cm?
长方形的长是15厘米，宽是8厘米，周长是多少厘米．
<gadget id="calculator">15 + 8</gadget>
<output>23</output>

<gadget id="calculator">23 * 2</gadget>
<output>46</output>

<result>46</result>