Probability, SM-Bank 041

Claire baked 18 cookies.

She baked equal numbers of chocolate chip, macadamia nut and plain cookies.

Claire randomly picked one of the cookies.

What are the chances it was chocolate chip or plain? (1 mark)
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Claire's brother ate a macadamia nut cookie. What are the chances that the next cookie Claire randomly selects is macadamia nut or plain? (2 marks)
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Show Answers Only

a. \(\dfrac{2}{3}\)

b. \(\dfrac{11}{17}\)

Show Worked Solution

a.	\(P\text{(choosing chocolate chip or plain)}\)	\(=\dfrac{\text{number of chocolate chip and plain}}{\text{total number of cookies}}\)
		\(=\dfrac{12}{18}\)
		\(=\dfrac{2}{3}\)

b.	\(P\text{(choosing macadamia or plain)}\)	\(=\dfrac{\text{number of macadamia and plain}}{\text{total number of cookies}}\)
		\(=\dfrac{5+6}{17}\)
		\(=\dfrac{11}{17}\)