Quote:
Originally Posted by SaGo
Can you please explain how you get 6!/2!*2!*2!
Especially the denominator?
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There is a formula for
Permutations of n items, some alike
From n items, of which p are alike of one kind, q are alike of another kind, and so on, the number of possible permutations is n!/ (p! * q!)
Comming bak to question:
In how many ways can the television director fill the
six time slots for commercials if the sponsor has
three different commercials, each of which is to be shown twice.
So, n = 6
and let 3 diffrent commercial be A, B and C (each of which is to be shown twice)
So we can safely say.. that the six required commercials are AA BB and CC
now applying the above stated formula.. p are alike of one kind ie, 2 (for A)
similarly q are alike of another kind ie, 2 (for B)
and r are alike of third kind ie, 2 (for C)
putting everything in formula:
n!/p!*q!*r!...
=> 6!/2!*2!*2! ie, 90.
HTH