Question 1191405: List all the permutations of the 4 objects a, b, c, and d, taken 2 at a time.
Answer by greenestamps(13200)   (Show Source):
You can put this solution on YOUR website!
I don't know what it is about this that you need help with....
The first letter can be any of the four given letters; for each first letter, the second letter can be any of the three remaining letters.
To make sure you get all the permutations, keep them in alphabetical order.
b --> ab
/
a - c --> ac
\
d --> ad
a --> ba
/
b - c --> bc
\
d --> bd
a --> ca
/
c - b --> cb
\
d --> cd
a --> da
/
d - b --> db
\
c --> dc
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