Problem-Solving and Data AnalysisHardConditional probability among instrument players
Problem-Solving and Data Analysis practice question
In a class of 60 students, 25 play a musical instrument, and 15 of those 25 also sing in the choir. If a student who plays an instrument is chosen at random, what is the probability that the student also sings in the choir?
Answer: 3/5 or 0.6 or 15/25
The condition restricts the choice to the 25 players: 15/25 = 3/5.
Common wrong answers
- If you answered 1/4
- 1/4 uses all 60 students as the denominator.
- If you answered 5/12
- 5/12 is 25/60, the share who play an instrument.
- If you answered 2/5
- 2/5 is the share of players who do not sing.
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