PaperTest GMAT - Numbers/Sets problem

For the positive numbers, n, n+1, n+2, n+4, and n+8, the mean is how much greater the median?

Answ: 1

My approach: let n=1, n+1=2, n+2 = 3, n+4 = 5, n+8 = 9
So median = 3
mean ( i assumed mean of the set) = (1+9) / 2 = 5
Difference = 5-3 = 2
Answer then = n+1 = 2

On the other hand, if i calculate mean as avg (1+2+3+5+9) / 5 = 4
Difference = 4 - 3 = 1
Answer = 1

Could someone explain his/her approach? What am I missing?

Thanks!!!