Statistic and Probability

Question

Jhude has 6 Algebra books and 4 Statistic books. He only has a space for 5 books on the shelf. If the first 3 slots are to be occupied by Statistics books and the remaining slots by the Algebra books, in how many ways can this be done?

Answer 1

If I interpret it to mean that the first book chosen goes into the first slot then you have:

slot 1: 4 ways (from 4 stat books)

slot 2: 3 ways (3 remaining stat books)

slot 3: 2 ways (2 remaining stat books)

slot 4: 6 ways (from 6 algebra books)

slot 5: 5 ways (5 remaining algebra books)

Total = 4*3*2*6*5