A parallelogram, the two adjacent sides are 2.5 cm and 1.5 cm respectively, what is its perimeter in cm?
一个平行四边形，相邻两边分别是2.5厘米，1.5厘米，它的周长多少cm．
<gadget id="calculator">2.5 + 1.5</gadget>
<output>4</output>

<gadget id="calculator">4 * 2</gadget>
<output>8</output>

<result>8</result>