Eleven animals of a circus have to be placed in eleven cages one in each cage. If 4 of the cages are too small for 6 of the animals, find the number of ways of caging the animals.
Large animals 6 Small animals 5
Large cages 7 Small cages 4
6 large animals can be cages in 7 large cages in 7p6=7!.
5 small animals can be caged in remaining 5 cages (4 small + 1 large) in 5! ways.
Hence the number of ways is
7!×5!=5040×120=604800.