P&C -4

JEE Main 2015 Coaching › Algebra questions › P&C -4

Number of permutations of 1,2,3,4,5,6,7,8 and 9 taken all at a time ,such that the digit
1 appearing somewhere to left of 2
3 appearing to the left of 4 and
5 somewhere to the left of 6
(e.g.815723946 would be one such permutation)

#Mathematics #Algebra

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2 Answers

333

Hardik Sheth ·2013-03-24 10:35:29

total no of permutations are 9 factorial...
out of these,1 will be to the left of 2 half the times...apply this thrice,divide by 8,and u get the ans..

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Anonymous how 1 will be to the left of 2 half the times??
Upvote·0·2015-11-22 09:32:16
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486

Niraj kumar Jha ·2013-03-24 07:43:44

Is the answer 9!/8?

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Swarna Kamal Dhyawala no it is 9x7!
Upvote·0· Reply ·2013-03-24 08:07:08
Swarna Kamal Dhyawala plzz explain it who ever gets answer
Upvote·0· Reply ·2013-03-24 08:07:45
Niraj kumar Jha 9!/8 and 9*7! are the same thing.
Upvote·0· Reply ·2013-03-24 08:19:53
Swarna Kamal Dhyawala ooo sorry i saw opposite ...but how did u do
Upvote·0· Reply ·2013-03-24 08:41:10
Anonymous please explain your answer
Upvote·0·2015-11-22 09:32:58
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