Posted by **Nada** on Tuesday, May 8, 2012 at 9:14am.

A teacher prepares 5 different books for 7 students.If each student can get one or no book from the teacher , find the number of ways of distributing the books among the students.

can u explain it to me detailly.i have thought about this question for serveral hours but i still cant get the answer

- Maths(permutation) -
**MathMate**, Tuesday, May 8, 2012 at 10:34am
This is a tricky question.

The teacher prepares 5 books for 7 students, but did not say that all five books HAVE to be distributed. So my interpretation is that 0 to 5 books could have been distributed.

For the case of 0 book distributed, there is only one way: no one gets any book.

For 1 book distrbuted, there are 7 ways to distribute, one for each student.

For 2 books distributed, there are 7 ways for the first book, 6 ways for the second. The order of the books is not important because they are different. There are 7!/(7-2)! ways.

Continue until all 5 books are distributed for a total of

1+7+42+210+840+2520=3620 ways

- Maths(permutation) -
**Nada**, Tuesday, May 8, 2012 at 11:31am
but the correct ans is 2520,why?

- Maths(permutation) -
**MathMate**, Tuesday, May 8, 2012 at 1:05pm
As I indicated, this is a trick question.

I have assumed that not all five books need to be distributed because the question says the teacher "prepares" 5 books, and any student can take "one or no book". It did not say he "distributes" 5 books.

The answer assumes ALL five books are distributed, as you can verify with the last entry on my list, or 7!/2!

## Answer This Question

## Related Questions

- math - Create two problems for your fellow students to solve. Make one of the ...
- English - Several __________ were left on their desks in the classroom during ...
- Math (combination/permutation) - Question 1: There are 12 students in a class. ...
- Math - Alegbra 2 some1 plz help? - in a certain math class, each student has a ...
- Math (combination/permutation) - Question 1: There are 12 students in a class. ...
- pre calc - A math teacher uses four algebra books, two geometry books, and three...
- maths - each of the students in a class writes a dirrerent 2 digit number on the...
- MATHS - Mrs.Koh purchased new books for the school library, of which 6 were ...
- Algebra - In a certain math class, each studen has a textbook, every two ...
- Combinations and Permutations, Steve and Ms. Sue☺ - 1. Solve: 6C3 **120 ...

More Related Questions