A bookstore classifies its books by reader group, type of book, and cost. What is the probability that a book selected at random is a child's book, given that it costs $15?

Pr (Cb) & Pr (cost $15) = 15 (Ncb) / (T1*T3)

Step-by-step explanation:

Classification of the book in to 3

First let's assign terms to each probability

Let:

T1 = total number of type of Reader's group

T2 = total number of Type of book

T3 = total number of type of Cost

Probability of child's book and cost $15 = Pr (Cb) & Pr (cost $15)

Then find probability of child's book and cost separately:

Pr of child's book = Pr (Cb)

Pr (Cb) = (number of child's book) / total number of type of group

Ncb = number of child's book

Pr (Cb) = Ncb/T1

Pr (cost $15) = $15 book/total number of cost

Pr (cost $15) = 15/T3

probability of child's book and cost $15 = Pr (Cb) * Pr (cost $15)

= Ncb/T1 * 15/T3

Pr (Cb) & Pr (cost $15) = 15 (Ncb) / (T1*T3)