This seems to be a very simple task, but I don’t know how it can be solved.

I have a lot of numbers: {1, 2, 3, 4, 5}. I need to calculate how many even 3-digit numbers I can get from these numbers.

The numbers in the number must not be repeated.

The first thing I want to do in this situation is to find the number of numbers that I can make up under a given condition.

It’s easy: 5 * 4 * 3 = 60

These are all numbers, but I only want the even ones.

For an hour now I have been unable to figure out how to solve this problem – even though it is simple.

I used an online application that generated all these 60 numbers, including 24 even ones.

If necessary, I will post it.

The question is: how to solve this problem mathematically?