How many ways are there to arrange 6 books on a shelf, if the 4 science books must be grouped together and the 2 english books must be grouped together?
The science books can be placed before or after the English books, so that’s two ways science-English or English-science. There are 24 ways to arrange the 4 science books and 2 ways to arrange the English books. So we have 24×2+2×24=96.
