Question

Let X = the number of nonzero digits in a randomly selected 4-digit PIN that has no restriction on the digits. What are the possible values of X? 0, 1, 2, 3, 4 0, 1, 2, 3, 4, ... 1, 2, 3, 4, ... 1, 2, 3, 4 0, 1, 2, 3

Answer 1

X = {0, 1, 2, 3, 4}

Explanation:

If X is the number of nonzero digits in a 4-digit PIN with no restriction on the digits, the pin can have up to 4 nonzero digits.

Let's see some examples:

If the PIN is 0000 then X = 4

If the PIN is 2045 then X = 3

If the PIN is 7546 then X = 0

From the previous examples, we can see that the possible values for X are 0, 1, 2, 3, 4.

Thus X = {0, 1, 2, 3, 4}