A combination lock has digits from 0 to 39. three numbers are required to open.
how many combinations are possible if you cannot repeat any digits?
40*39*38 = 59280
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How many combinations are possible if you cannot have the same digit twice in a row?
Call the number F, S, and T for 1st, 2nd, and 3rd
F is 1/40
S is any but F, = 1/39
T is any but S, = 1/39
40*39*39 = 60840