Problem-Solving and Data AnalysisVery hardConditional probability from survey counts
Problem-Solving and Data Analysis practice question
In a survey of 200 people, 120 own a car, and 90 of those also own a bicycle. Of the 80 people who do not own a car, 50 own a bicycle. If a person who owns a bicycle is chosen at random from the survey, what is the probability that the person also owns a car?
Answer: 9/14
140 people own a bicycle, and 90 of them own a car, so the probability is 90/140 = 9/14.
Common wrong answers
- If you answered 9/20
- 9/20 divides by all 200 people instead of the 140 bicycle owners.
- If you answered 3/4
- 3/4 is the probability that a car owner owns a bicycle.
- If you answered 5/14
- 5/14 is the probability that a bicycle owner does not own a car.
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