The lengths of the three sides of an isosceles trapezoid are 10 cm, 30 cm, and 50 cm respectively, and its upper base is the longest side. What is the perimeter of the isosceles trapezoid in cm?
一个等腰梯形的三条边长分别10厘米、30厘米、50厘米，而且它的上底是一条最长的边，那么这个等腰梯形的周长是多少厘米．
<gadget id="calculator">30 * 2</gadget>
<output>60</output>

<gadget id="calculator">50 + 10 + 60</gadget>
<output>120</output>

<result>120</result>