Problem-Solving and Data AnalysisHardProbability from two overlapping groups
Problem-Solving and Data Analysis practice question
In a class of 50 students, 30 play football. Of those 30, 20 also swim. Of the 20 students who do not play football, 10 swim. If a student is chosen at random from the class, what is the probability that the student swims?
Answer: 3/5 or 0.6 or 30/50
Swimmers: 20 + 10 = 30 of 50.
Common wrong answers
- If you answered 2/5
- 2/5 counts only the footballers who swim.
- If you answered 2/3
- 2/3 is the share of footballers who swim, the wrong denominator.
- If you answered 1/5
- 1/5 counts only the non-footballers who swim.
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