Bunuel
Official Solution:
The probability that a convenience store has cans of iced tea in stock is 50%. If James stops by 3 convenience stores on his way to work, what is the probability that he will not be able to buy a can of iced tea?
A. \(\frac{1}{8}\)
B. \(\frac{1}{4}\)
C. \(\frac{1}{2}\)
D. \(\frac{3}{4}\)
E. \(\frac{7}{8}\)
James won't be able to buy a can of iced tea if none of the stores has it. Since the probability that a convenience store has cans of iced tea is \(\frac{1}{2}\) then the probability that a convenience store does not have cans of iced tea is also \(\frac{1}{2}\), (\(1-\frac{1}{2}=\frac{1}{2}\)), so \(P(NNN)=( \frac{1}{2} )^3=\frac{1}{8}\).
Answer: A
WHAT IS WRONG WITH THE FOLLOWING APPROACH?
The probability that he will be able to buy a can of iced tea after visiting third store is 1/2*1/2*1/2=1/8.
so the probability that he wont be able to buy = 1-1/8=7/8?