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 350,000 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:

Five marbles are in a bag: two are red and three are blue. If Andy randomly picks two of the marbles, what is the probability that at least one of the marbles he chooses will be red.

Five marbles are in a bag: two are red and three are blue. If Andy randomly picks two of the marbles, what is the probability that at least one of the marbles he chooses will be red.

1.) 2/5 2.) 6/10 3.) 7/10 4.) 15/20 5.) 19/20

Vote for 3)

Andy pick 2 out of 5 without replacing the marbles back into the bag. The chances of picking up 2 blue marbles are 3/5*1/2=3/10, thus the probability pikcing up at least 1 red marble is 1-3/10=7/10.

can you see why we have different results, while our approaches are directly reverse? You come from behind and I'm from the front. Both correct. Can't see the problem.

Five marbles are in a bag: two are red and three are blue. If Andy randomly picks two of the marbles, what is the probability that at least one of the marbles he chooses will be red.

1.) 2/5 2.) 6/10 3.) 7/10 4.) 15/20 5.) 19/20

P(Atleast one red) = 1- probablity (no red)
= 1 - 3/5
= 2/5

P(Atleast one red) = 1- probablity (no red) = 1 - 3/5 = 2/5

Krisrini, it's a smart way of doing it..

I calculated this as Probability that both are red + Probability that one is read = 2/5*1/4 + 2/5 * 3/4 = 2/20 + 6/20 = 2/5

It should be 7/10.

Probability of no reds is not 3/5. It is 3/5 *2/4 = 3/10
1 - Prob of red = 1 - 3/10 = 7/10

Different approach:
- There are 5 balls, thus there are 5C2 ways to pick 2, or (5*4)/2! = 10.
- There are 3C2 ways to pick only blues (3*2)/2! = 3.
- (Total combinations) - (combinations with no reds) = 10 - 3 = 7
- Therefore, 7/10 is the prob of picking at least 1 red.

Hello everyone! Researching, networking, and understanding the “feel” for a school are all part of the essential journey to a top MBA. Wouldn’t it be great... ...

Booth allows you flexibility to communicate in whatever way you see fit. That means you can write yet another boring admissions essay or get creative and submit a poem...