Find the number of ways in which two books on economics and three books on accountancy can be arranged in a row

$2!\times 3!=12$

The correct answer is $120$, Can anyone explain how?

  • 2
    $\begingroup$ $5!$ is the number of ways. You have 5 possibilities for the first book, 4 possibilities for the 2nd bood, and so on. $\endgroup$
    – Wuestenfux
    Commented Jun 10, 2017 at 15:57

2 Answers 2


For the first book, you have $5$ possibilities: first place, second place... fifth place.

For the second book, only four possibilities (since you have already placed book number one).

For the third book, three.

The fourth book, two.

And the last one does not give you any choice.

So $$5\times 4\times 3\times 2=5!=120$$

possibilities to arrange your books.


You have 5 total books, so the number of arrangements is $5!=120$.


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