There are 2 things:

1. Choosing the rotors: Say choosing 3 from 5 rotors. That will be 5*4*3 or 5C3.

2. Positioning the rotors: Once we have chosen the rotors, they can be permuted. 3 rotors would be 3! i.e. 6 different ways.

## Rotor: Choosing & Positioning

There are 2 things:

1. Choosing the rotors: Say choosing 3 from 5 rotors. That will be 5*4*3 or 5C3.

2. Positioning the rotors: Once we have chosen the rotors, they can be permuted. 3 rotors would be 3! i.e. 6 different ways.