Answer:
72000
Explanation:
First five digit number is 10000
And the last five digit number is 99999.
There are 99999-10000+1 five digits in all.
That simplifies to 89999+1=90000.
Any number whose units digit is 5 or 0 is divisble by 5.
10000 is the first five digit number that is divisble by 5.
10000+5k where k is a positive integer can be used to find any after.
The last five digit number divisible by 5 is 99995. What is k then?
10000+5k=99995
5k=89995
k=89995/5
k=17999
How many 5 digit numbers are divisble by 5?
So the first one happens at k=0 and the last one happens at k=17999.
How many numbers is that? 17999+1=18000.
So the number of 5 digit numbers that aren't divisble by 5 is 90000-18000=72000