It is known that the upper and lower bases of an isosceles trapezoid are 9 cm long and 12 cm long, and the waist length is 5 cm. What is its circumference in cm?
已知一个等腰梯形的上下底分别长9厘米、12厘米，腰长5厘米，那么它的周长是多少厘米．
<gadget id="calculator">5 * 2</gadget>
<output>10</output>

<gadget id="calculator">10 + 9 + 12</gadget>
<output>31</output>

<result>31</result>