Use the five numbers 1.2.3.4.5 to form a three digit number without repetition. How many even numbers are there?

Use the five numbers 1.2.3.4.5 to form a three digit number without repetition. How many even numbers are there?

The number of bits can only be 2 or 4,
Ten choose from the remaining four,
The hundred choose from the remaining three
So the answer is 2 * 4 * 3 = 24