Question

Your personal library contains books written by 165 authors. 60% of the authors are men. 40% of the authors write only nonfiction works. Also, 40 of the male authors write only nonfiction works. Assuming that your library has only one book by each author, what is the probability that a book picked at random is either a work written by an author who writes only nonfiction or a work written by a man?

Answer 1

60% of the authors are men
so 0.60 * 165 ---> # of male authors

same logic with 40% of the authors being nonfiction writers
0.40 * 165 ---> # of nonfiction authors

now, for the last step, we need to subtract the authors who are male *and* write only nonfiction work. (40). that way, no author is double-counted.

then divide by the total # of authors to get the probability