The conversation between human and AI assistant.
How many two-digit numbers can you form using the digits 1,2,3,4,5,6,7,8 and 9 without repetition?
How did you calculate that?
Well, there are 9 choices for the first digit and 8 choices for the second digit (since we can't repeat any digit). So we can form 9 x 8 = 72 two-digit numbers.