In how many ways can, 3 books on computer, 3 books on Economics and 5 books on commerce be arranged, if the books of each subject are kept together.

In how many ways can 4 books of math and 3 books of English and 5 books of sociology be arranged on a shelf so that (a) same subject are together (b) only sociology books are kept together (c) only English books are kept together

In how many ways can 5 keys be put in a ring?

In how many ways can 5 boys and 5 girls sit in a circle so that no two boys sit together?

The number of ways in which n books can be arranged on a shelf so that two particular books are not together is

In how many ways can 6 boys and 6 girls sit in a round table so that no two boys sit together

In how many ways can 7 examination papers be arranged so that papers 6 and 7 are never together?

In how many ways can 21 English and 19 Hindi books be placed in a row so that no two hindi books are together?