Question

How many different numbers are possible?

A personal identification number consists of 3 letters followed by 3 digits. The letters X, Y, and Z are not used and the last digit cannot be 0 or 9.

Answer 1

Each of the first 3 letters can be chosen from the 23 letters, {A, B, C, …, U, V, W}, so there are 23³ possible choices.

The first 2 digits can be any number from {0, 1, 2, …, 9}, so there are 10² choices.

The last digit cannot be 0 or 9, so you can select from {1, 2, 3, …, 8} which gives 8 choices.

Then the total number of PINs that you can make is

23³ × 10² × 8 = 9,733,600