The mobile red flag of a class is an isosceles triangle. Its perimeter is 100 cm, and the length of one of its waists is twice the length of the base. What is the length of the base of this triangle in cm?
一个班的流动红旗是等腰三角形，它的周长是100厘米，它的一条腰长是底边长的2倍，这个三角形底边长是多少厘米？
<gadget id="calculator">2 + 2 + 1</gadget>
<output>5</output>

<gadget id="calculator">100 / 5</gadget>
<output>20</output>

<result>20</result>