Permutation and CombinationHard
Question
You are given 8 balls of different colour (black, white,...). The number of ways in which these balls can be arranged in a row so that the two balls of particular colour (say red & white) may never come together is:
Options
A.8! - 2.7!
B.6. 7 !
C.2. 6 !. 7C2
D.none
Solution
Required number of possible is
8 ! - 2. 7 ! = 7 ! (8 - 2) = 6 . 7!
2 . 6 ! . 7C2
8 ! - 2. 7 ! = 7 ! (8 - 2) = 6 . 7!
2 . 6 ! . 7C2
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