[JEE Advanced 1992] 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 ____
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
VAVidaara Admin
✓ Vidaara Team
✓ Accepted
· 1mo 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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