Question

1. At a college library exhibition of faculty publications, 3 different mathematics books, 4 different social science books, and 3 different biology books will be displayed on a shelf. In how many ways can these ten books be arranged on the shelf if all books on the same subject are identical?

Answer 1

10! / (4! * 3! * 3!)

Answer 2

At the start of the question you say something like 3 <b>different </b> math books, but at the end
you say all books on the same subject are identical, so which is it?

Assuming that each subject's books are indistinguishable, we have a formula for this

number of arrangements = 10!/(3!4!3!) = .....