题目内容：

英语翻译
If the length of the segment AB is 1,M is the midpoint of the segment AB,and point C divides the segment MB into two parts such that MC:CB=1:2,then the length of AC is

优质解答

如果一线段AB的长度为1,M是该线段AB的重点,C把线段MB分成两部分,其中MC：CB=1:2,那么线段AC长是多少?
MC：CB=1:2 => BC=2/3 *MB
MB=1/2 *AC=1/2 => BC=1/3
AC=AB-BC=1-1/3=2/3