There are 120 of them.
There are 31 of them.
How many
10000
There are 125 of them.
Not couting 1 and 1000, there would be 998 numbers.
Infinitely many. The number pi , for example, is between 1 and 1000 and, since pi is a transcendental number, it contains infinitely many digits. Plus, there are all the irrational numbers - each with infinitely many digits, and all the rationals with recurring decimals - again with infinitely many digits.
10 of 1 digit, 45 of 2 digits and 120 of 3 digits making 175 in all.
2625
1000
There are 120 of them.
How many strings of three digits are there? 000 to 999, or a total of 1000. How many strings of three digits contain the same three digits? That's 000, 111, 222 ... 999! ten in total. The difference is your answer: 1000-10 = 990.
That would be 118644... / 1000... (follow the 1 by as many zeroes as there are digits after the decimal point in your number).
There is only 1, the number 54.
10001
123
2890