How many ways can 4 men and 4 women sit in a row of 8 seats such that no two men sit together?
Assume that all people are distinguishable. So if Fred and Ted switch places, it's a different formation.
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First seat all the males. This can be done in 4 ! = 2 4 ways. Now, observe that there are 3 gaps between the 4 men (excluding the empty gaps at the left and right side of the leftmost and the rightmost men). So, we need to fill these with 3 women out of the 4. This again can be done in 4 ! = 2 4 ways. Finally, the last woman can now be place in any of the 5 remaining gaps (now, including the before excluded empty gaps).
So, the final answer is 4 ! 2 ⋅ 5 = 2 8 8 0