Question

A college bookstore has two identical mathematics texts, three identical physics texts, four identical computer science texts, and two identical psychology texts in a row on a shelf. If a student knocks them all on the ground and then hurriedly places them all back on the shelf with no attention to their original order, in how many ways can he replace the texts on the shelf?

Answer 1

69,300 ways

Explanation:

mathematics texts, = 2

Physics texts = 3

Computer science tests = 4

Psychology texts = 2

The total number of books

= 2+3+4+2

= 11

Next we have to calculate the number of ways that these books can be placed back on this shelf.

11!/2!3!4!2!

11! = 39916800

2! = 2

3! = 6

4! = 24

2! = 2

39916800/2*6*24*2

= 39916800/576

= 69300 ways

He can replace the texts in 69300 ways.