Question

Jane is choosing a 3 -letter password from the letters A, B, C, D, and E. The password cannot have the same letter repeated in it. How many such passwords are possible?

Answer 1

There are 5 possible letters. The first letter can be any of them, so there are 5 possible first letters. For each of the five first letters, there are four possible second letters because there cannot be any repeats. For each of the four second letters, there are three third letters because there cannot be any repeats. Thus the total number of passwords is 5*4*3=60.