90
There are 167960 9 digits combinations between numbers 1 and 20.
50 to the 5th power.156,250 combination.
10 Combinations (if order doesn't matter). 3,628,800 Possiblilities (if order matters).
how many combinations of 4 numbers are there in 7 numbers
Number of 7 digit combinations out of the 10 one-digit numbers = 120.
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.
There are 840 4-digit combinations without repeating any digit in the combinations.
7
56 combinations. :)
Any 6 from 51 = 18,009,460 combinations
5
45.
There are 9 1-digit numbers and 16-2 digit numbers. So a 5 digit combination is obtained as:Five 1-digit numbers and no 2-digit numbers: 126 combinationsThree 1-digit numbers and one 2-digit number: 1344 combinationsOne 1-digit numbers and two 2-digit numbers: 1080 combinationsThat makes a total of 2550 combinations. This scheme does not differentiate between {13, 24, 5} and {1, 2, 3, 4, 5}. Adjusting for that would complicate the calculation considerably and reduce the number of combinations.
90
There are 167960 9 digits combinations between numbers 1 and 20.
120 combinations using each digit once per combination. There are 625 combinations if you can repeat the digits.