There are books on Mathematics, andon physics. In how many ways these be placed on shelves if the books on the same subject area to be together?
The number of ways these are placed on shelves if the books of same subject to be together:
Number of ways to arrange mathematics books together
Number of ways to arrange physics books together
The total number of ways is calculated as follow:
Hence, the number of ways these are placed on shelves if the books of same subject to be together is .