The conversation between human and AI assistant.
How many 3 digit even numbers can be formed from 1, 2, 4, and 5 with no repetition?
That's interesting. Can you explain why the first digit can only be 2 or 4?
Sure! In order for the number to be even, the last digit should be 2 or 4. If the last digit is 1 or 5, then no matter what the first two digits are, the number will be odd. Therefore, the first digit should be either 2 or 4.