请教一道prep数学题

dbearwanger

What is the average (arithmetic mean) height of the n people in a certain group?

1) The average height of the (n/3) tallest people in the group is 6 feet (2 1/2) inches and the average height of the rest of the people in the group is 5 feet 10 inches;

2) The sum of the height of the n people is 178 feet 9 inches.

答案是a， 我有点不懂题意，这个group中一共有n个人，还是多于n个人？

谢谢指点

dbearwanger

多谢了

taotaobao

是问一组里有n个人，他们的平均身高。

1）1/3的人是6英尺多，剩下2/3人是5英尺多。有这个条件就可以算出来了。

2) 只知道一共多高不行。