Sadie is wrapping a gift. She can choose from among 12 different patterns of gif

Question

Sadie is wrapping a gift. She can choose from among 12 different patterns of gift wrap, 9 different colors of ribbon, and 15 different gift tags. Only one of each category will be used to prepare the gift. Each combination of gift wrap, ribbon, and gift tags is equally likely.

a) How many ways can Sadie prepare the gift?

b) If 5 of the gift wraps are shiny and 3 of the ribbons are shiny, what is the probability that the birthday

present will have both shiny wrapping paper and shiny ribbon?

c) If 5 of the gift wraps are shiny and 3 of the ribbons are shiny, what is the probability that the birthday

present will have shiny wrapping paper OR shiny ribbon?

d) 7 of the gift tags are birthday tags. This gift is for a birthday, if Sadie just grabs a gift tag without looking at

it, what is the probability the prepared gift has an appropriate tag?

Explanation / Answer

a) Number of ways = 12*9*15 = 1620

b) P(Shiny wrapping paper and shiny ribbon) = 5*3*15/1620 = 5/36

c) P(Shiny wrapping paper or shiny ribbon) = (5*9*15 + 12*3*15 - 5*3*15)/1620 = 11/18

d) P(Birthday gift tag) = 7/15

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