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MC II-B Combinatorics problem 9.25 b) solution wrong ?

 
 
LuMichael的头像
MC II-B Combinatorics problem 9.25 b) solution wrong ?
LuMichael - 2018年02月17日 Saturday 07:59
 

Question 9.25:

Suppose you are dealt three cards from a standard deck of cards.

Part b):

Find the probability the first two cards are clubs, given that the third card drawn is a club.

In the solution for part b), when you solve the case P(B int A^c)=39/52 · 38/51 · 13/50 + 39/52 · 13/51 · 12/50 + 13/52 · 38/51 · 12/50 = 401/1700. 

13/52 · 38/51 · 12/50 corresponds to the case where the first card is a club, the second card isn't a club, and the third card is a club. When you calculate when the second card isn't a club, I think it should be 39/51. 

I believe the correct answer to the question is 22/425 (as opposed to 22/423).


 
ReynosoDavid的头像
Re: MC II-B Combinatorics problem 9.25 b) solution wrong ?
ReynosoDavid - 2018年02月20日 Tuesday 13:03
 

You are correct, it should be $\frac{39}{51}$, as none of the non-club cards have been used yet. The handout is now updated.

Thank you for letting us know!