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题库 / Prep2007E2-DS-133
What is the average (arithmetic mean) height of the n people in a certain group?
(1) The average height of the ~$\frac{n}{3}$~ tallest people n the group is 6 feet ~$2\frac{1}{2}$~ inches, and the average height of the rest of the people n the group is 5 feet 10 inches.
(2) The sum of the heights of the n people is 178 feet 9 inches.
Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
EACH statement ALONE is sufficient.
Statements (1) and (2) TOGETHER are NOT sufficient.
还没有题目讲解（毕出老师会陆续发布对官方考题的解读，请保持关注）。
(1)avg height=(n/3*平均身高1+2n/3*平均身高2）/n，n可以直接被消掉
(2)avg height=总身高/n n未知！
没看懂题目。。。
注意n可以被消掉，不能想当然
好具有代表性的一道题
这题啥意思啊。。。n/3 tallest people n the group is XXX. 比如n=5, 就是5/3最高的人?
n是未知数，2求不出平均身高的具体值