### Instruction: How many whole numbers between 99 and 999 contain exactly one 0?### Response: I need to find all the three-digit numbers that have one 0 in their decimal representation.
The 0 could be in the hundreds place, the tens place, or the ones place.
But it can't be in the hundreds place, because then the number would start with 0 and not be a three-digit number.
So the 0 has to be in the tens place or the ones place.
If the 0 is in the tens place, then the number looks like x0y, where x and y are non-zero digits.
There are 9 choices for x, from 1 to 9, and 9 choices for y, from 1 to 9.
So there are 9 times 9, or 81, numbers of this form.
If the 0 is in the ones place, then the number looks like xy0, where x and y are non-zero digits.
There are 9 choices for x, from 1 to 9, and 9 choices for y, from 1 to 9.
So there are another 9 times 9, or 81, numbers of this form.