How many 4 digits codes are possible using the numbers 0 -9 only once?

Expert Answers
justaguide eNotes educator| Certified Educator

The codes have to be prepared using the numbers 0-9 and are 4 digit long. Also, each of the numbers can be used only once

We have 10 choices for the first digit.

As there are no repetitions, there are 9 choices for the second digit, 8 choices for the third digit and 7 choices for the fourth digit.

In all, the number of codes that can be created are 10*9*8*7 = 5040

The number of 4 digit codes possible using the numbers 0-9 only once is 5040.