10^4 or 10,000, assuming that 0000 is a valid number. 0000, 0001, 0002, ..., 9997, 9998, 9999.
Well honey, the numbers between 99 and 3000 are inclusive, so you gotta count 'em all. To find out how many three-digit numbers there are, you subtract the first three-digit number (100) from the last three-digit number (999) and add 1, giving you a grand total of 900 three-digit numbers. So, buckle up and start counting, darling!
45
I assume you mean how many 4-digit numbers can be made from a set such as {A,A, B, C} where A, B and C are single digits. There are 12 such numbers.
6
162
about 13
6: 146, 164, 416, 461, 614, and 641.
Assuming you mean permutations of three digits, then the set of numbers that can be made with these digits is: 345 354 435 453 534 543 There are six possible permutations of three numbers.
10
1
1,956 different numbers can be made from 6 digits. You can calculate this by using the permutation function in a summation function, like this: Σ6k=1 6Pk = 6P1+6P2+...+6P5+6P6 What this does is calculate how many 1 digit numbers you can make from 6 digits, then how many 2 digit numbers can be made from 6 digits and adds the amounts together, then calculates how many 3 digit numbers can be made and adds that on as well etc.
10 digits are numbers in the billions.