Almost got me on this one. 20 numbers but 29 digits
744 digits.
There are 167960 9 digits combinations between numbers 1 and 20.
630 digits.
36
There are the digits 1 through 9 for the first digit. Then, we have 0 through 9 for the second digit - excluding the first digit. For the third digit, we have 0 through 9 excluding the two previous digits
There are 2892 digits.
192 digits
the main purpose of multiplication is to multiply 1 through as many digits as you want. :)
You would get 9 single digits. You would get one digit for 1 through 9 and the rest of the numbers would be more than one digit.
There are 2700 digits.
11522
This can be solved by looking at each set of digit lengths. From 1 through 9, it's obvious there are 9 digits. From 10 through 99, there are 2 digits for each of the 90 numbers, so that makes 90*2=180 digits. Next, from 100 to 400, there are 401 numbers with 3 digits each, making another 401*3=1,203 digits. So the final answer is 9+180+1,203 = 1,392 digits.