The answer explains that there are 10 two-digit positive multiples of nine.
The number of positive multiples of nine that are two-digit numbers is 10.
- List out the two-digit multiples of nine: 18, 27, 36, 45, 54, 63, 72, 81, 90,99.
- The next multiple of 9 is 108 but it is three digit number. So, 99 is the highest two digit number which are multiples of 9.
- Count the total, which is 10 multiples of nine that are two-digit numbers.
Therefore, there are 10 positive two-digit numbers which are multiples of nine.
