Saturday, November 14, 2009

Help for permutation n combination pls?

Mr Bean buys a box of 12 begonia plants. the label on the box indicates that 6 of the plants will have red flowers and 6 will have pink flowers. However, none of the plants are in bloom. If Mr Bean plants the begonias in a horizontal row,





how many different colour arrangements are possible when all the begonias are in bloom?








Thanks

Help for permutation n combination pls?
answer: 12!/(6!*6!)





solution:





there can be 12! ways of arranging 12 different things linearly, however there are 6 of one type and 6 of other type ...hence, after avoiding repetetions due to similarities we get the answer.





another example:





take the word "SEEK" how can we arrange in different ways...2 Es and 1S, 1K


SEEK


EESK


KEES


SKEE


KSEE


EEKS


ESEK


EKES


SEKE


KESE


ESKE


EKSE





i.e., 4!/(2!*1!*1!) = 12 ways


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