A bookstore sells books in several formats—hardcover, paperback, digital, and audio.
Based on past sales, the table below gives the estimated probabilities that a randomly selected purchase will be of particular types.
Hardcover Paperback Digital Audio
0.17 0.35 0.41 0.07
(a) If a purchase is selected at random, what is the probability that this purchase is for a book that is digital or audio?
(b) If a purchase is selected at random, what is the probability that this purchase is for a book that is not digital?
(c) If a purchase is selected at random, what is the probability that this purchase is for a book that is a printed book?
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(a) The probability that a purchase is for a book that is digital or audio is the sum of the probabilities for digital and audio:
P(digital or audio) = P(digital) + P(audio) = 0.41 + 0.07 = 0.48
So, the probability that a purchase is for a book that is digital or audio is 0.48.
(b) The probability that a purchase is for a book that is not digital can be found by subtracting the probability of a digital purchase from 1:
P(not digital) = 1 - P(digital) = 1 - 0.41 = 0.59
So, the probability that a purchase is for a book that is not digital is 0.59.
(c) The probability that a purchase is for a book that is a printed book (hardcover or paperback) is the sum of the probabilities for hardcover and paperback:
P(printed book) = P(hardcover) + P(paperback) = 0.17 + 0.35 = 0.52
So, the probability that a purchase is for a book that is a printed book is 0.52.
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