Events & Promotions
|
|
GMAT Club Daily Prep
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
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Apr 2610:00 AM EDT
-11:00 AM EDT
The Target Test Prep course represents a quantum leap forward in GMAT preparation, a radical reinterpretation of the way that students should study. Try before you buy with a 5-day, full-access trial of the course for FREE!
Apr 2711:00 AM EDT
-12:00 PM EDT
Prefer video-based learning? The Target Test Prep OnDemand course is a one-of-a-kind video masterclass featuring 400 hours of lecture-style teaching by Scott Woodbury-Stewart, founder of Target Test Prep and one of the most accomplished GMAT instructors
Apr 2808:00 AM PDT
-11:00 AM PDT
Whether you are just beginning your MBA journey or fine-tuning your path to a 700+ score, GMAT Day is designed to give you a competitive edge.
24 Aug 2009, 09:53
Kudos
Bookmarks
A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
65%
(hard)
Question Stats:
50% (03:26) correct
50%
(03:16)
wrong
based on 6
sessions
History
Date
Time
Result
Not Attempted Yet
OPEN DISCUSSION OF THIS QUESTION IS HERE: a-certain-jar-contains-only-b-black-marbles-w-white-marbles-104924.html
Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Problem Solving (PS) Forum
Still interested in this question? Check out the "Best Topics" block below for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
24 Aug 2009, 10:05
Kudos
Bookmarks
from 1) i can reduce it to b < (w+r) but this doesnt give any relation between w & r ...i m klueless 
24 Aug 2009, 10:12
Kudos
Bookmarks
I posted an explanation of why the first statement is sufficient a while back on another forum, so I'll just paste that here:
There are quite a few ways to look at this problem, though it's actually based on an idea we encounter all the time in day to day life. I'll suggest two approaches:
If you know the concept of 'odds' from probability (and from real life), then the first statement is clearly sufficient here. If you say that "the odds are 21 to 5 in favor of picking a consonant when you pick a random letter from the alphabet", that is just a ratio of the number of ways to pick a consonant to the number of ways to not pick a consonant. From those odds, we can see that the probability of picking a consonant is 21/26, and the probability of picking a vowel is 5/26.
That's what statement 1 is telling us: the odds of getting a red marble are better than the odds of getting a white marble (the fraction on the left is the ratio of red marbles to non-red marbles, while the fraction on the right is the ratio of white marbles to non-white marbles). If the odds are higher, the probability must be higher.
Alternatively, you could look at this abstractly. We don't need to rewrite the fractions at all. We know that:
r/(b + w) > w/(b + r)
and all of the letters represent positive quantities. We also know that if a fraction has *both* a larger numerator and a smaller denominator than another, it must be larger in value. Looking at the above inequality, it's impossible for w to be greater than r; if it were, then the fraction on the right would have both a larger numerator and a smaller denominator than the fraction on the left. So r must be greater than w (they can't be equal, if that inequality is true), which is all we need to know here.
There are quite a few ways to look at this problem, though it's actually based on an idea we encounter all the time in day to day life. I'll suggest two approaches:
If you know the concept of 'odds' from probability (and from real life), then the first statement is clearly sufficient here. If you say that "the odds are 21 to 5 in favor of picking a consonant when you pick a random letter from the alphabet", that is just a ratio of the number of ways to pick a consonant to the number of ways to not pick a consonant. From those odds, we can see that the probability of picking a consonant is 21/26, and the probability of picking a vowel is 5/26.
That's what statement 1 is telling us: the odds of getting a red marble are better than the odds of getting a white marble (the fraction on the left is the ratio of red marbles to non-red marbles, while the fraction on the right is the ratio of white marbles to non-white marbles). If the odds are higher, the probability must be higher.
Alternatively, you could look at this abstractly. We don't need to rewrite the fractions at all. We know that:
r/(b + w) > w/(b + r)
and all of the letters represent positive quantities. We also know that if a fraction has *both* a larger numerator and a smaller denominator than another, it must be larger in value. Looking at the above inequality, it's impossible for w to be greater than r; if it were, then the fraction on the right would have both a larger numerator and a smaller denominator than the fraction on the left. So r must be greater than w (they can't be equal, if that inequality is true), which is all we need to know here.
