5 boys (call them A,B,C,D,E) place their books in a bag. The 5 books are are drawn out in random order and given back to the 5 boys. What is the probability that exactly 3 boys will receive their original book?

Dear ankit,

Select three of the five boys who will get their own books.
. . There are: . ways.

The other two boys have simply switched books: . way.

Hence, there are: . ways for 3 boys to get their own books.


There are: . ways to return the books.


Therefore: .

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