ID Numbers A company’s employee ID number system consists of one letter followed by three digits. How many different ID numbers are possible with this system?

To find:

The possible number of different employee IDs in a company.

Given:

A company’s employee ID number system consists of one letter followed by three digits.

Approach:

If two events E1 and E2 occur in order and E1 occur in m ways and E2 occur in n ways, then the two events can occur in order in m×n ways.

The consequence of the fundamental counting principle is for any number of events; that is, if E1, E2, E3….. EK are events that occur in order and E1 occur in n1 ways,