### How many 4 digit numbers can be formed using the digits 1 3 5 7 9?

Using only the numbers 1,3,5,7,9, and using each number only once, we have 5 options for the first digit, then 4 remaining options for the second, 3 remaining options for the third and 2 remaining options for the fourth. This means there are 5x4x3x2 ways to combine the digits 1,3,5,7,9 into a 4 digit number. 5x4x3x2=120, so there are 120 four digit numbers that can be made.

### How many six digit numbers can be formed using the digits 0123456789 Example equals 123456 or 098765?

The number of six digit numbers that you can make from ten different digits if repetitions of same digit on the six digit number is allowed is 1 000 000 numbers (including number 000 000). If no repetitions of the the same digit are allowed then you have: 10P6 = 10!/(10-6)! = 151 200 different six digit numbers (six digit permutations form 10 different digits).

### How many 2 digit numbers can be formed using number 1 2 3 4 such that each number contains number 1?

### How many 3-digit numbers can be formed using 0123456789 when repetition is not allowed?

Assuming a 3-digit number does not start with a zero (ie a 3-digit number is one of 100-999): There are 9 possibilities for the first digit (1-9); for each of these there are 9 possible remaining numbers for the second digit; for each of these there are 8 possible remaining numbers for the last digit; giving 9 x 9 x 8 = 648 possible numbers.

### How many four digits numbers can be formed using 0123456789?

Assuming that the first digit of the 4 digit number cannot be 0, then there are 9 possible digits for the first of the four. Also assuming that each digit does not need to be unique, then the next three digits of the four can have 10 possible for each. That results in 9x10x10x10 = 9000 possible 4 digit numbers. If, however, you can not use the same number twice in completing the 4 digit…

### How many four digit numbers can be formed using the digits 0123456789 if the repetitions of digits are allowed?

If you don't mind beginning the 4-digit number with one or more zeros, then there are 10 choices for each digit, and the total number of possibilities is: (10 x 10 x 10 x 10) = 10,000 . If the 4-digit number can't begin with a zero, then there are only 9 choices for the first digit, but 10 choices for each of the others, and the total number of possibilities is: (9 x 10…