SOLUTION: How many ways can a 2 Physics books, 4 Mathematics books and 3 Chemistry books be arranged on a shelf if all books of the same subject may be arranged in any order but must be toge

There are 2! =  2 permutations inside the block of 2 Physics books;

          4! = 24 permutations inside the block of 2 Math books;  and

          3! =  6 permutations inside the block of 3 Chemistry books.


Also, there are 3! = 6 permutations of these 3 blocks as whole items.


THEREFORE, the are  2*24*6*6 = 1728 different permutations under the posed conditions, in all.