How many 4-digit personal identification numbers are possible if the number cannot contain a zero?

Question

Mathematics

Cello

23 June, 04:55

How many 4-digit personal identification numbers are possible if the number cannot contain a zero?

+1

Answers (1)

Know the Answer?

Mckenzie Pena · Answer 1

It is given that we cannot include zero in the 4 digit PIN. So, we have only nine numbers with us, namely, 1,2,3,4,5,6,7,8 and 9.

Now, there are two possible cases for this question.

Case 1: If a digit can be used only once. i. e digits can not be repeated.

Then, the number of cases are 9*8*7*6 = 3024 possible PIN numbers.

Case 2: If a digit can be used again. i. e digits can be repeated.

Then, the number of cases are 9*9*9*9 = 6561 possible PIN numbers.