SOLUTION: How many ways can 5 people A, B, C, D, E sit in a row if A must be to the left of B but not necessarily next to each other?
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Question 1117733: How many ways can 5 people A, B, C, D, E sit in a row if A must be to the left of B but not necessarily next to each other? Answer by greenestamps(13200) (Show Source):
Consider the 5!=120 ways the 5 people can sit in a row.
For every arrangement in which A is to the left of B, there is an arrangement with all the other people in the same places but with A and B switched, so that B is to the left of A.
So exactly half of the 120 arrangements have A to the left of B.
