If the adjacent sides of a parallelogram are 7 cm and 9 cm long, what is its perimeter in cm?
平行四边形相邻两边长7厘米和9厘米，它的周长多少厘米．
<gadget id="calculator">7 + 9</gadget>
<output>16</output>

<gadget id="calculator">16 * 2</gadget>
<output>32</output>

<result>32</result>