Average of all 6 digit numbers that contain only digits $1,2,3,4,5$ How do I find the average of all $6$ digit numbers which consist of only digits $1,2,3,4$ and $5$?
Do I have to list all the possible numbers and then divide the sum by the count? There has to be a more efficient way, right?
Thank you!

$$(111111+111112+\cdots+555555)=$$
$$(100000\times 5^5+200000\times 5^5+\cdots+500000\times 5^5)+(10000\times 5^5+20000\times 5^5+\cdots+50000\times 5^5)+\cdots+(1\times 5^5+2\times 5^5+\cdots+5\times 5^5)$$
