let's do puzzles: logic game #19

A bank manager must change the four letter security code of the bank vault every day. The same code change cannot be used on consecutive days. Each day after the bank closes the manager must change the code in exactly one of three ways:

   Change 1- Each letter in the code is moved one space to the left, with the far left letter moving to the far right.
   Change 2- The letters Q and T change places, and the letters R and S change places.
   Change 3 - The letters Q and R change places, and the letters S and T change places.

Solution: it is important to work out the possibilities at the initial sketch examination.

Day 1 start- QRST
Day 2 #1 - RSTQ
Day 3 #2 - SRQT

QRST
#1  RSTQ
#2 QTSR

QRST
2 TSRQ
1  SRQT

QRST
2 TSRQ
3 STQR

QRST
3 RQST
1  QTSR

QRST
3 RQTS
2 STQR

Even if the order of the same combos changes, the final result is the same.

Q22. How many different codes could three be after two changes have been made?

(A) 1
(B) 2
(C) 3
(D) 4
(E) 5

(C) correct 3

The trick was that the order of the changes did not matter in this game.