A bookshelf contains 9 mysteries, 7 biographies, and 4 science fiction books. A book is randomly selected, not replaced, then another is selected. Find the probability of selecting a biography then a mystery.

63/380

Step-by-step explanation:

Initially,

# of Mysteries, M = 9

# of Biographies, B = 7

# of Sci. Fiction, S = 4

Total number of books = 9 + 7 + 4 = 20 books

P (first book selected is biography) = 7/20

After selecting 1 biography book,

# of Mysteries, M = 9

# of Biographies, B = 7 - 1 = 6

# of Sci. Fiction, S = 4

Total number of books remaining = 9 + 6 + 4 = 19 books

P (second book selected is a mystery) = 9/19

Hence (P first book is biography and 2nd book is mystery)

= (7/20) (9/19)

= 63/380

63/380