Question

There are 3 copies each of 4 different books. Find the number of ways of arranging them on a shelf.

Answer 1

Total number of books = 3 × 4 = 12 

Each of the 4 different titles has 3 copies each 

∴ Required number of ways of arranging them on a shelf = \(\frac{12!}{3!3!3!3}\) = \(\frac{12!}{(3!)^4}\) = 369600.