Question

11. a television store owner figures that 45 percent of the customers entering his store will purchase an ordinary television set, 15 percent will purchase a plasma television set, and 40 percent will just be browsing. if 5 customers enter his store on a given day, what is the probability that he will sell exactly 2 ordinary sets and i plasma set on that day?

Answer 1

Using the binomial distribution:
P(2 out of 5 buy ordinary TV) = $5C2 \times 0.45^{2} \times0.55^{3} =0.337$
P(1 out of 5 buy plasma TV =$5C1\times0.45\times0.55 ^{4} =0.206$
The events are mutually exclusive, therefore the probability of both occuring is:  0.337 + 0.206 = 0.543