5 boys (call them A,B,C,D,E) place their books in a bag. The 5 books areare drawn out in random order and given back to the 5 boys. What is theprobability 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: .

We are all IITians and here to help you in your IIT JEE preparation.

All the best.

 If you like this answer please approve it....

win exciting gifts by answering the questions on Discussion Forum

Approved