The perimeter of an isosceles triangle is 40 cm, and the length of the waist is twice the length of the base. What is the length of the waist in cm?
一个等腰三角形的周长是40厘米，腰长是底边长的2倍，它的腰长是多少厘米．
<gadget id="calculator">40 / 5</gadget>
<output>8</output>

<gadget id="calculator">8 * 2</gadget>
<output>16</output>

<result>16</result>