If the width of a rectangle is 56 cm and the length is twice the width, what is the perimeter of the rectangle in cm?
一个长方形的宽是56厘米，长是宽的2倍，这个长方形的周长是多少厘米．
<gadget id="calculator">56 * 2</gadget>
<output>112</output>

<gadget id="calculator">112 + 56</gadget>
<output>168</output>

<gadget id="calculator">168 * 2</gadget>
<output>336</output>

<result>336</result>