Question

How many different 4-digit personal identification numbers are possible if no digit can be used twice? a. 1,000 b. 5,040 c. 9,000 d. 10,000 Please select the best answer from the choices provided A B C D.

Answer 1

✅ B. 5,040

i got it right ⬇️

Answer 2

b.

Explanation:

There are 10 digits 0 - 9.

Using the formula for r permutations from n:

nPr = n!/ (n - r)!

- so the answer would be 10! / (10 - 4)!

= 5040.