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The probability that Tom will win the Booker prize

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saxenankit
 Post subject: The probability that Tom will win the Booker prize
 Post Posted: Tue Feb 22, 2011 7:14 am 
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Students


Posts: 69
The probability that Tom will win the Booker prize is 0.5, and the probability that John will win the Booker prize is 0.4. There is only one Booker prize to win. What is the probability that at least one of
them wins the prize?
(A) 0.2
(B) 0.4
(C) 0.7
(D) 0.8
(E) 0.9

Source: Nova Maths
OE: C

As per my calculation it should be = 0.5 + 0.4 - 0.0 = 0.9

since only 1 can win the award, thus the AND probability should be 0. (Mutually Exclusive events).

Please comment.
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RonPurewal
 Post subject: Re: The probability that Tom will win the Booker prize
 Post Posted: Tue Feb 22, 2011 7:18 am 
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ManhattanGMAT Staff


Posts: 7146
saxenankit wrote:
The probability that Tom will win the Booker prize is 0.5, and the probability that John will win the Booker prize is 0.4. There is only one Booker prize to win. What is the probability that at least one of
them wins the prize?
(A) 0.2
(B) 0.4
(C) 0.7
(D) 0.8
(E) 0.9

Source: Nova Maths
OE: C

As per my calculation it should be = 0.5 + 0.4 - 0.0 = 0.9

since only 1 can win the award, thus the AND probability should be 0. (Mutually Exclusive events).

Please comment.


um, yeah. if there's only one prize, then they're mutually exclusive, so you can just add the probabilities.

0,7 would be the correct probability if these were independent events, but they aren't, so it's not.
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shantascherla
 Post subject: Re: The probability that Tom will win the Booker prize
 Post Posted: Fri Feb 25, 2011 10:22 pm 
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Course Students


Posts: 21
What is the correct answer ? .7 ?
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RonPurewal
 Post subject: Re: The probability that Tom will win the Booker prize
 Post Posted: Sat Feb 26, 2011 4:48 am 
Offline
ManhattanGMAT Staff


Posts: 7146
shantascherla wrote:
What is the correct answer ? .7 ?


the way the problem is currently written, the answer is definitely 0,9.

if the author had intended a different solution, then he/she didn't write the problem correctly.
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