Problem: Given the set of n numbers; n>1, of which one is 1−n1 and all the others are 1. The arithmetic mean of the n numbers is:
Answer Choices:
A. 1
B. n−n1
C. n−n21
D. 1−n21
E. 1−n1−n21
Solution:
Let s be the sum and M(=ns) be the arithmetic mean of the given numbers. Since the number of 1 's is n−1,s=(n−1)(1)+1−n1=n−n1
∴M=nn−n1=1−n21