Expert: Josh - 12/16/2003

Question
how many 3 digit numbers can you create with 3, 6, 7 and 9 using each digit only once in each number?

Answer
How many digits "_,_,_,_" can we create?

Number of ways to fill the first digit is 4, since we have four elements to choose from {3,6,7,9}.

Whichever digit it is, after it has been selected, it will be eliminated from the list. This results in a smaller list containing only 3 digits.

Again, number of ways of picking the second digit from a list of three is 3.

Now, removing this second digit gives us a list containing two elements.

There can be only 2 possible outcomes in selecting the third digit from this list.

Finally, whatever remains must occupy the last digit.

Taking the product of these, we get 4*3*2*1=24 different possible numbers.

3679
3697
3769
3796
3967
3976

6379
6397
6739
6793
6937
6973

7369
7396
7639
7693
7936
7963

9367
9376
9637
9673
9736
9763

Cheers:)