A rectangular piece of paper is 15 cm long and 9 cm wide. What is the perimeter of this rectangle in centimeters?
一个长方形纸张，长是15厘米，宽是9厘米．这个长方形的周长是多少厘米？
<gadget id="calculator">15 + 9</gadget>
<output>24</output>

<gadget id="calculator">24 * 2</gadget>
<output>48</output>

<result>48</result>