Since we are interested in two-digit numbers, we need to consider all the numbers between 10 and 99, which are 99-10=89 numbers; however, as we need to include the number 10, there are 99-9=90 numbers in the sequence.
Notice that the first number, 10, is an even number, the next one, 11, is odd, and so one.
Thus, half of the numbers are even, and the other half consists of odd numbers.
Finally, the answer is that 90/2=45 numbers are odd.