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Arrange Letters

by bharti.2010 » Tue Dec 13, 2011 9:18 am
Source: Kaptest
In how many different ways can the letters A, A, B, B, B, C, D, E be arranged if the letter C must be to the right of the letter D?

A.1,680
B.2,160
C.2,520
D.3,240
E.3,360
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by shankar.ashwin » Tue Dec 13, 2011 9:34 am
Total 8 letters with 2 A's and 3B's.

No of ways to arrange them = 8!/(2!*3!) = 3660

In exactly half the arrangements C will be to the right of D (or) 1680
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by chieftang » Tue Dec 13, 2011 11:48 am
shankar.ashwin wrote:Total 8 letters with 2 A's and 3B's.

No of ways to arrange them = 8!/(2!*3!) = 3660

In exactly half the arrangements C will be to the right of D (or) 1680
Correction: 3360. :)
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by CappyAA » Tue Dec 13, 2011 12:10 pm
chieftang wrote:
shankar.ashwin wrote:Total 8 letters with 2 A's and 3B's.

No of ways to arrange them = 8!/(2!*3!) = 3660

In exactly half the arrangements C will be to the right of D (or) 1680
Correction: 3360. :)
Good catch - I think that was probably a typo though. At least he arrived at the right answer! I got 1680 too.
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