Okay to solve this problem you would simply do this solution. It took me a minute, haven't had to do integers in a while. :D
From 10,000 to 99,999 the numbers divisible by 5 ends in 0 or 5.
The first (most significant) digit can be any of nine from 1 to 9.
The 2nd digit can be any of 10.
The 3rd digit can be any of 10.
The 4th digit can be any of 10.
The 5th digit can be either of 2.
That's 9(10)(10)(10)2=18,000
I hope this helps.
