what is the average height of the people in a certain group?
（1）the average height of the 3/n tallest people in the group is 6 feet 2.5 inches, and the average height of the rest of the people in the group is 5feet 10 inches.
（2）the sum of the heights of the n people is 178feet 9 inches.
答案选A 我觉得选D。。。。求真相。。。。作者: hangtianyuan 时间: 2010-9-5 19:11
楼主题目都打错了。。。n/3
the average=(n/3 *a +2n/3 *b)/n=a/3+2b/3
A is sufficient作者: judyenglishS 时间: 2010-9-6 20:56
