If the distance between two adjacent sides of a quadrilateral is 15 cm and 12 cm, what is its perimeter in cm?
一块平行边四形相邻两条边的距离是15厘米和12厘米，它的周长是多少厘米．
<gadget id="calculator">15 + 12</gadget>
<output>27</output>

<gadget id="calculator">27 * 2</gadget>
<output>54</output>

<result>54</result>