Count them
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.
How many times does the digit 1 occur in ten place in the numbers from 1 to 1000?
999-111=888 888 3 digit numbers can be made with numbers between 1 - 9
There are 900 three-digit whole numbers between 1 and 1000
There are 9 digits that can be the first digit (1-9); for each of these there is 1 digit that can be the second digit (6); for each of these there are 10 digits that can be the third digit (0-9); for each of these there are 10 digits that can be the fourth digit (0-9). → number of numbers is 9 × 1 × 10 × 10 = 900 such numbers.
3
There are 2941 4-digit numbers such no two of its digits differ by 1.
There are 28706 such combinations. 5456 of these comprise three 2-digit numbers, 19008 comprise two 2-digit numbers and two 1-digit numbers, 4158 comprise one 2-digit number and four 1-digit numbers and 84 comprise six 1-digit numbers.
There are 90 two-digit whole numbers between 1 and 100.
The pages of a book are numbered from 1 to 128. How many page numbers contain the digit 6?
There are 90 two-digit numbers... starting with 10 and ending with 99.
Not sure what a "didget" is. It is possible to make 18 5-digit numbers.