Four digit number can be formed using 0,1,2,3,4,5,6,7,8,9
Any number which ends with 0 or 5 is divisible by 5.
_ _ _ _ We have to check for 4 digit numbers. The 4 digit number must end with 0 or 5.
So the number at the thousandth place can be written in 9 ways (since 0 can not be written at thousandth place) = 9
the number at the hundredth place can be written in 10 ways = 10
the number at the tenth place can be written in 10 ways = 10
the number at the unit place can be written in 2 ways = 2
So the number of ways the 4 digit number can be written as (9)(10)(10)(2) = 1800 ways.
For total number of ways:
the number at the thousandth place can be written in 9 ways = 9
the number at the hundredth place can be written in 10 ways = 10
the number at the tenth place can be written in 10 ways = 10
the number at the unit place can be written in 10 ways = 10
Total number of ways = (9)(10)(10)(10) = 9000 ways
So the number of ways the 4 digit number can be written that can be divisible by 5 = Total number of ways - number of ways the 4 digit number can be written
The number of ways the 4 digit number can be written that can be divisible by 5 = 9000 - 1800 = 7200 ways
