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​