Find the arithmetic mean of all the three-digit palindromes. (Recall that a palindrome is a number that reads the same forward and backward, such as 777 or 383) 

Recall that the arithmetic mean of all the ‘n’ digit palindromes is just the average of the largest and smallest ‘n’ digit palindromes, and in this cases the 2 palindromes are 101 and 999 $\frac{101+999}{2}=550$ and 550 is the final answers