Probability Question from the Sets

[rajkoneru]

Each participant in a certain study was assigned a sequence of 3 different letters from the
set {A, B, C, D, E, F, G, H}. If no sequence was assigned to more than one participant
and if 36 of the possible sequences were not assigned, what was the number of
participants in the study? (Note, for example, that the sequence A, B, C is different from
the sequence C, B, A.)
A. 20
B. 92
C. 300
D. 372
E. 476

Can you please help.

[yamini]

Selecting 3 characters out of 8, in which order has to be considered.

So it is permutation.
8P3 - 8!/(8-3)! = 8*7*6 = 336 permutations are possible.

As 36 permutations are not assigned to any body 336-36 = 300 students. (c)