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.
Nov 1912:30 PM EST
-01:30 PM EST
Learn how Keshav, a Chartered Accountant, scored an impressive 705 on GMAT in just 30 days with GMATWhiz's expert guidance. In this video, he shares preparation tips and strategies that worked for him, including the mock, time management, and more
Nov 2007:30 AM PST
-08:30 AM PST
Learn what truly sets the UC Riverside MBA apart and how it helps in your professional growth
Nov 2001:30 PM EST
-02:30 PM IST
Learn how Kamakshi achieved a GMAT 675 with an impressive 96th %ile in Data Insights. Discover the unique methods and exam strategies that helped her excel in DI along with other sections for a balanced and high score.
Nov 2211:00 AM IST
-01:00 PM IST
Do RC/MSR passages scare you? e-GMAT is conducting a masterclass to help you learn – Learn effective reading strategies Tackle difficult RC & MSR with confidence Excel in timed test environment- Nov 23
11:00 AM IST
-01:00 PM IST
Attend this free GMAT Algebra Webinar and learn how to master the most challenging Inequalities and Absolute Value problems with ease. 
Nov 2407:00 PM PST
-08:00 PM PST
Full-length FE mock with insightful analytics, weakness diagnosis, and video explanations!
Nov 2510:00 AM EST
-11:00 AM EST
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.
11 Aug 2017, 12:37
Kudos
Bookmarks
Hi brandmanrocks,
To start, you have to always be sure that you are answering the question that is ASKED (sometimes the question is so specific that there's really only one way to approach it). That having been said, most prompts can be approached in more than one way, so you could certainly approach this prompt in the way that you described. However, you have to make sure to 'adjust' your 'math' to account for how you approached the work.
You can certainly treat this question as a permutation, BUT you then have to keep track of every potential option that 'fits' what is asked for....
(4 choices)(3 choices) = 12 possible options in which the order matters. Of the various 'pairs', there would be TWO that 'fit' what we're looking for:
(X+Y)(X-Y)
(X-Y)(X+Y)
Again, we would have to count that as two options because 'your way' is focused on treating this as a permutation.
2/12 = 1/6 so you end up with the same correct answer as you would if you treated this as a 'Combination' question.
GMAT assassins aren't born, they're made,
Rich
To start, you have to always be sure that you are answering the question that is ASKED (sometimes the question is so specific that there's really only one way to approach it). That having been said, most prompts can be approached in more than one way, so you could certainly approach this prompt in the way that you described. However, you have to make sure to 'adjust' your 'math' to account for how you approached the work.
You can certainly treat this question as a permutation, BUT you then have to keep track of every potential option that 'fits' what is asked for....
(4 choices)(3 choices) = 12 possible options in which the order matters. Of the various 'pairs', there would be TWO that 'fit' what we're looking for:
(X+Y)(X-Y)
(X-Y)(X+Y)
Again, we would have to count that as two options because 'your way' is focused on treating this as a permutation.
2/12 = 1/6 so you end up with the same correct answer as you would if you treated this as a 'Combination' question.
GMAT assassins aren't born, they're made,
Rich
06 Jan 2020, 05:31
Kudos
Bookmarks
Actually it is selecting two( (x+y) and (x-y)) out of four
Therefore the probability is 2/4 = 1/2
Therefore the probability is 2/4 = 1/2
06 Jan 2020, 16:51
Kudos
Bookmarks
charanvemasani
Hi charanvemasani,
Unfortunately, that is NOT how 'probability math' works. We're given the terms (X+Y), (X+5Y), (X-Y) and (5X-Y). We're asked for the probability that multiplying any randomly chose pair will give a result that is written in the format: X^2 - (BY)^2.
Since there are only 4 terms, and we're MULTIPLYING, there are only 6 possible outcomes.
From the prompt, you should notice that the 'first part' of the result MUST be X^2....and that there should be NO 'middle term'....which limits what the first 'term' can be in each of the parentheses....
By brute-forcing the 6 possibilities, you would have...
(X+Y)(X+5Y) = X^2 + 6XY + 5Y^2
(X+Y)(X-Y) = X^2 - Y^2
(X+Y)(5X-Y) = X^2 + 4XY - Y^2
(X+5Y)(X-Y) = X^2 + 4XY - 5Y^2
(X+5Y)(5X-Y)= 5X^2 +24XY - 5Y^2
(X-Y)(5X-Y) = 5X^2 -6XY + Y^2
Only the second option is in the proper format, so we have one option out of six total options.
Final Answer:
GMAT assassins aren't born, they're made,
Rich
