36
The sum of the number of digits in all the numbers between 31 and 400 inclusive is 1041.
180
I assume you mean significant digits. All digits are significant. A zero between other digits is always significant.
The answer is 498 digits (you're not suppose to count 1 and 500) if this question was intended to ask "how many numbers are there between 1 and 500?"
There are 6484 digits BETWEEN the two given numbers.
36
223
123
One million is 1 followed by 6 zeroes - a total of 7 digits.
The sum of the number of digits in all the numbers between 31 and 400 inclusive is 1041.
I believe here are 51 such numbers.
Typically one letter followed by seven numbers.
180
You have seven different digits (symbols) to choose from, so you can form seven different one digit numbers and 7×7=72=49 different two digit numbers.
There are 167960 9 digits combinations between numbers 1 and 20.
I assume you mean significant digits. All digits are significant. A zero between other digits is always significant.