Question

Susan is choosing a 2-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

slot method

2 slots possible
1st slot has 5 choices: A,B,C,D,E
2nd has 4 choices since 1 was already chosen for the first slot

so total is 5*4 or 20 diffferent passwords

Answer 2

1st letter can be any of 5 letters

2nd letter can be 5-1 any of 4 letters

5*4 = 20

there are 20 possible passwords