Question

Suppose account numbers for an internet service provider consist of alpha-numeric characters. The first character is a digit (0 through 9). The next 4 characters are capital letters (A through Z) and the last four characters are digits.

How many account numbers are possible if no digit appears more than once?

Answer 1

20,442,240 possible account numbers.

Explanation:

First character has 10 possibilities.

Next 2 has 26 x 26=676 possible combinations.

The last 4 has 9x8x7x6 = 3024 possible combinations.

The answer would be 10 x 676 x 3024

= 20,442,24.

Hope this helps.