In an isosceles triangle ABC, the length of AB is twice that of AC. If its circumference is 200 cm, what is the length of BC in cm?
等腰三角形ABC中，AB的长是AC的两倍，如果其周长是200厘米，那么BC长是多少厘米．
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">1 + 1 + (1/2)</gadget>
<output>5/2 = around 2.5</output>

<gadget id="calculator">200 / (5/2)</gadget>
<output>80</output>

<result>80</result>