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Good Question on P and C

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Good Question on P and C

by jayanti » Sat Jul 23, 2011 11:06 pm
Six alphabets A B C D, have to be arranged in six numbered positions (1-6). How many ways can you arrange them so that neither A is in the position numbered 1, nor B is in position numbered 2 and C is in position numbered 4.
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by knight247 » Sat Jul 23, 2011 11:54 pm
You're right. Have edited my post. Let me just work this one out and get back to you.
Last edited by knight247 on Sun Jul 24, 2011 1:25 am, edited 1 time in total.
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by jayanti » Sun Jul 24, 2011 1:02 am
Shouldn't 426 be the answer!!

1. A should not be in position number 1.
No. of ways in which A occurs in position 1 = 5! = 120 arrangements.
Therefore possible arrangements = 6! - 120 = 600 arrangements.

2. B should not be in position number 2.
No. of ways in which B occurs in position 2 = 5! = 120 arrangements.
But in this case, A occurs in position 1 by 24 ways which is already included in the first case.
Therefore possible arrangements after including second constraint = 600-120 + 24 = 504 arrangements.

3. C should not be in position 3:
No. of ways in which C occurs in position 3 = 5! = 120 arrangements.
In this case also A occurs in position 1 by 24 ways which is already included in the first case.
Also B occurs in position 2 by 18 ways (actually it's also 24 ways but ABC can occur in 6 ways which is already included), which is already included in the second case.

Therefore total arrangements after considering all constraints = 504-120+24+18 = 426

I hope that the answer is correct. comments please
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