72. (with the range of two digit numbers being from 10 to 99).
All of them.
All of the odd numbers between 11 and 99 inclusive are two digit numbers that are not multiples of 2. There are 45 of them.
19 times10,11 (is 2),12,13,14,15,16,17,18,19,21,31,41,51,61,71,81 and 91
The answer will depend on how many digits there are in each of the 30 numbers. If the 30 numbers are all 6-digit numbers then the answer is NONE! If the 30 numbers are the first 30 counting numbers then there are 126 combinations of five 1-digit numbers, 1764 combinations of three 1-digit numbers and one 2-digit number, and 1710 combinations of one 1-digit number and two 2-digit numbers. That makes a total of 3600 5-digit combinations.
There is no such ratio that applies for all single-digit and double-digit integers.
-2
The answer depends on what is implied by "such".
There are 45 such numbers.
17
1
It would help to know which digit. 0 appears in 9 numbers and each of the others in 18 numbers.
When a person writes all 4-digit numbers, they range from 1000 to 9999, totaling 9000 numbers. The digit '2' can appear in each of the four positions (thousands, hundreds, tens, and units). In each position, '2' will appear 900 times (e.g., for the thousands place, numbers from 2000 to 2999), leading to a total of 3600 occurrences of the digit '2' across all four positions.