[JEE Advanced 1992] four coloured balls and four boxes of matching colours the number of ways to
Four coloured balls and four boxes of matching colours. The number of ways to place one ball per box so no ball is in its own-colour box is ____
1 Answer
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· 2d ago
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Answer: $9$.
This is the derangement $D_4=9$.
JEE Advanced 1992 · Permutations and Combinations — verified solution by the Vidaara Team.
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