even numbers instead of odd numbers An island people does not use odd numbers.  instead of counting 1,2,3,4,5,6 they count as 2,4,6,8,20,22....what number they use instead of 111?

for 50, they use 400, so for 100 they use 800, so for 811 they should use 822.  Is there any easy way to find this other than this?
 A: I guess it is sufficient to compute the numbers to base 5 and then replace the digits 0,1,2,3,4 by 0,2,4,6,8.
So $111= 4*5^2 + 2*5^1 +1*5^0$ yields the representation 421 and then you get 842 as a result.

More generally, if they only use $k$ symbols as digits, than the way they count is exactly the same as counting to base $k$, where we can replace the symbols by the first $k$ numbers $\{0,1..,k-1\}$. 
In case you don't know, it is true for every natural number $k$ that every natural number $n$ has a unique representation as a sum of weighted powers of $k$, where the coefficients are all part of $\{0,...,k-1\}$ - this is precisely meant by the representation of $n$ to the base of $k$.
In your case, you have distinct $5$ digits, so the rest follows.
BTW, you made a mistake in the last row, since you used $1$ as a digit while it is not allowed. Therefore $842$ is the real result.
A: Your table revealed the key  there is a pattern for 4 numbers on a sequence such as n+n+2+n+4 +n+6 and then it stops and we + 12 and then we go back to our 4 sequence (look horizontal line , second line ) and if you look to the 4th line , horizontally you will see that the same pattern is repeated , but as you may have seen in the 1 st line it is in 1+1 form and it turns out that the organization manner is :
1+1 form
n+n+2+n+4 +n+6 and then it stops and we + 12 and then we go back to our 4 sequence
1+1 form .....
So I would conclude in the fact that they would use 112 instead of 111 , cause if you look at the number 110 in your table , before the last line , at right , you will see that to make it continue to the 111 , in this case 112 , you would have to sum 2 , cause that is the pattern ,see fourth line and second line .
