Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

Prob that Sally will not win = 4/5 Prob that Jeny will not win = 4/5

Hence 4/5 * 4/5 = 16/25

correct?

Can someone explain the flaw here?

5 women are in a race. What is the probability that Sally and Jenny both will not win the race?

Say S,J, X1,X2,X5 are in the race.. [ assuming the only one person will win the race out of 5 with equal probablity] All these events[Winning S, Winning J, Winning X1.] are "mutually exclusive" --> Out comes are not common. P(S) = 1/5 P(J) =1/5 P(X1)=1/5 P(X2)=1/5 P(X3)=1/5

probability of either one of them winning hte race = P(S or J or X1 or X2 or X3) =P(S) +P(J)+P(X1)+P(X2)+P(X3) =1 probability that Sally and Jenny both will not win the race = probability that either one of X1 or X2 or X2 them win the race = P(X1)+P(X2)+P(X3) =1/5+1/5+1/5=3/5

What is the probability that Sally and Jenny both will not win the race?

What is the probability that Sally, but not Jenny, will win the race?

Guess the question wording is not correct logically...

2 people can not win a race together... hence instead of saying..."probability that Sally and Jenny both will not win the race".. it should be "probability that Sally or Jenny both will not win the race"

Even with the second question - it should be - "What is the probability that Sally, will win the race?"... we don't need to specify not Jenny.. as Sally and Jenny cannot win the race at the same time
_________________

Cheers! JT........... If u like my post..... payback in Kudos!!

|Do not post questions with OA|Please underline your SC questions while posting|Try posting the explanation along with your answer choice| |For CR refer Powerscore CR Bible|For SC refer Manhattan SC Guide|

~~Better Burn Out... Than Fade Away~~

gmatclubot

Re: combinatorics - Sally and Jenny
[#permalink]
16 Feb 2010, 13:41

Best Schools for Young MBA Applicants Deciding when to start applying to business school can be a challenge. Salary increases dramatically after an MBA, but schools tend to prefer...

Marty Cagan is founding partner of the Silicon Valley Product Group, a consulting firm that helps companies with their product strategy. Prior to that he held product roles at...