Question

Jasem wrote down all the 5 digit numbers that contained only the digits 1, 2, 3, 4 and 5. How many numbers were exactly divisible by 5?

Answer 1

There are `24` such numbers.

Explanation:

To solve tthis task we have to think "how does a number divisible by `5` look like?"

A number is divisible by `5` if it has either `0` or `5` as the units digit.

So from the given set it can only be: `----5` where the dashes replace any digits between `1` and `4`. Those digits can be chosen in `4! =1xx2xx3xx4=24` ways.

So finally: There are `24` numbers divisible by `5` among the numbers written by Jasem.