Enigma Machine Rotors

Computer Science Level 1

How many rotor configurations would an Enigma machine encrypter be able to select from if they needed to choose 3 rotors from a set of 10 rotors? (The order of the rotors matters).

Here is a set of three Enigma rotors Here is a set of three Enigma rotors

Image Credit: Emigma rotor set Wapcaplet .
760 10 60 940 10! 720 362

Karleigh Moore by Karleigh Moore , 27, USA

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2 solutions

Karleigh Moore
May 10, 2016

Order of the rotors matters here. In the first slot, there are 10 10 rotors to pick from, in the second there are 9 9 rotors to pick from, and in the third slot there are 8 8 rotors to pick from. Therefore, 10 × 9 × 8 = 720 10 \times 9 \times 8 = 720 .

7 Helpful 6 Interesting 5 Brilliant 0 Confused
Adi Pratama
May 11, 2016

Relevant wiki: Combinatorics Overview

Combination 10 of 3

10C3

0 Helpful 0 Interesting 0 Brilliant 1 Confused

So answer is 120

Hemanth K - 4 years, 10 months ago

The order matters. hence it is not Combinations problem. Instead it's a Permutation problem.

Puneet Pinku - 1 year, 3 months ago

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