The upper base of an isosceles trapezoid is 6 cm, the lower base is twice as long as the upper base, and the waist is equal to the lower base. What is the perimeter of this isosceles trapezoid in cm?
一个等腰梯形的上底是6厘米，下底是上底的2倍，腰和下底相等．这个等腰梯形的周长是多少厘米．
<gadget id="calculator">6 * 2</gadget>
<output>12</output>

<gadget id="calculator">6 + 12 + 12 + 12</gadget>
<output>42</output>

<result>42</result>