An isosceles trapezoid has an upper base of 6.5 cm, a lower base of 8.5 cm, and a waist of 4 cm. What is the perimeter of this trapezoid in centimeters?
一个等腰梯形，它的上底长6.5厘米，下底长8.5厘米，腰长为4厘米．这个梯形的周长是多少厘米？
<gadget id="calculator">6.5 + 8.5 + 4 + 4</gadget>
<output>23</output>

<result>23</result>