Common Core: S-MD.3
Problem 27 of 45s12-027
A claw machine gives a prize on 20% of plays, independently. Ana plays 5 times. What is the probability she wins exactly 2 prizes?
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Solution walkthrough2:10
- Binomial check: each play is win or lose, plays are independent, is fixed, every time.
- Use with , , , .
- One order, WWLLL: .
- The wins can be any of the plays: orders, each just as likely.
- Add the equal orders: .
- Traps: is one order only, swaps and , and is .