If the length of a rectangle is 35 cm and the width is 15 cm, what is its perimeter?
一个长方形的长是35厘米，宽是15厘米，它的周长是多少．
<gadget id="calculator">35 + 15</gadget>
<output>50</output>

<gadget id="calculator">50 * 2</gadget>
<output>100</output>

<result>100</result>