Re: A certain gallery is hanging a series of 7 paintings. All th
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31 Mar 2018, 20:50
this is the question of permutation.
we can solve it my multiplying factors method.
there are 7 positions for painting.
and the painting C1 C2 C3 C4 C5 P1 P2 (c represents canvas and P represents panel)
_ _ _ _ _ _ _
1 2 3 4 5 6 7
we start from the restriction: position 2 has two possibilities (P1 AND P2).
then position 6 has one possibility (either P1 or P2 depending upon which one is hung in position 2).
then position 1 has 5, position 3 has 4,position 4 has 3 position 5 has 2 and subsequently position 7 has 1 option.
so ans: 5*2*4*3*2*1*1=240 ans