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.
E
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
35%
(medium)
Question Stats:
69% (01:28) correct
31%
(01:04)
wrong
based on 672
sessions
History
Date
Time
Result
Not Attempted Yet
What is x?
(1) x = 4y - 4
(2) xy = 8
(1) x = 4y - 4
(2) xy = 8
My question is that why the answer is E instead of C. Any help would be appreciated.
What is x?
1) x=4y-4
2) xy=8
The solution given in the MGMAT guide explains that because after substitution, there are two different answers y = -1 and y = 2 which makes x = -8 and x = 4.
Since we can solve x with two statements together, why isnt the answer C? Instead of E (both statements together are not sufficient). Thanks in advance.
What is x?
1) x=4y-4
2) xy=8
The solution given in the MGMAT guide explains that because after substitution, there are two different answers y = -1 and y = 2 which makes x = -8 and x = 4.
Since we can solve x with two statements together, why isnt the answer C? Instead of E (both statements together are not sufficient). Thanks in advance.
Updated on: 04 Jul 2020, 06:48
Originally posted by BrentGMATPrepNow on 16 Oct 2016, 08:41.
Last edited by BrentGMATPrepNow on 04 Jul 2020, 06:48, edited 1 time in total.
Last edited by BrentGMATPrepNow on 04 Jul 2020, 06:48, edited 1 time in total.
Kudos
Bookmarks
yashrakhiani
Target question: What is the value of x?
Statement 1: x = 4y − 4
1 equation with 2 variables means there are infinitely many possible values for x.
If we're uncertain, we can TEST some values.
There are several values of x and y that satisfy statement 1. Here are two:
Case a: x = 0 and y = 1. in this case x = 0
Case b: x = 4 and y = 2. in this case x = 4
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT
Statement 2: xy = 8
1 equation with 2 variables means there are infinitely many possible values for x.
If we're uncertain, we can TEST some values.
There are several values of x and y that satisfy statement 2. Here are two:
Case a: x = 1 and y = 8. in this case x = 1
Case b: x = 4 and y = 2. in this case x = 4
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT
Statements 1 and 2 combined
Statement 1 tells us that x = 4y − 4
Statement 2 tells us that xy = 8
Take x = 4y − 4, and solve for y.
So, add 4 to both sides to get: x + 4 = 4y
Divide both sides by 4 to get: (x + 4)/4 = y
Now take xy = 8 and replace y with (x + 4)/4 to get...
(x)(x + 4)/4 = 8
Multiply both sides by 4 to get: (x)(x + 4) = 32
Expand: x² + 4x = 32
Set equal to zero to get: x² + 4x - 32 = 0
Factor: (x + 8)(x - 4) = 0
So, EITHER x = -8 OR x = 4
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT
Answer: E
General Discussion
26 Nov 2013, 21:49
Kudos
Bookmarks
The often forgotten qualification to the "n variables, n distinct equations" rule is that the equations must be linear. The second equation in the problem you provided will not plot a line. Rather, it plots a hyperbola.
So, the rule does not apply here. Hope that helps!
So, the rule does not apply here. Hope that helps!
