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http://papers.xtremepapers.com/CIE/Cambridge International A and AS Level/Mathematics (9709)/9709_w12_qp_63.pdf
Q6 c)
plz explain how u get this answer..
okay look
let's assume these 8 lines below are the 8 tiles
__ __ __ __ __ __ __ __
the question states that each of the tiles has an equal probability so p(black) = p(white) = p(grey) = 1/3
now the restriction is that we can't have two tiles of the same colour placed next to each other.
so let's assume that the first tile is black, hence the next one can either be grey OR white ( 1/3 + 1/3) = 2/3
since there are 7 tiles we have to place after the first one we simply do (2/3)^7
(each of the 7 remaining tiles only have an option of 2 colours, the first could be any of the three)
Hope it helped !