How many three-digit numbers can be generated from 1, 2, 3, 4, 5, 6, 7, 8, 9 such that the digits are in ascending order?

To solve this problem, we need to select three distinct digits from the set of nine available digits.

The key point is that for any three different digits chosen, there is only one possible way to arrange them in ascending order. For example, if we pick 5, 2, and 8, the only valid number is 258. Since the order is fixed by the ascending rule, we do not need to worry about permutations.

Therefore, the number of such three digit numbers is simply the number of ways to choose 3 digits out of 9, which is calculated using the combinations formula 9C3.

9C3 equals 9 multiplied by 8 multiplied by 7, divided by 3 multiplied by 2 multiplied by 1. 9 times 8 times 7 is 504. 3 times 2 times 1 is 6. 504 divided by 6 equals 84.

The correct answer is 84.