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 2212:30 AM EDT
-01:30 AM EDT
At one point, she believed GMAT wasn’t for her. After scoring 595, self-doubt crept in and she questioned her potential. But instead of quitting, she made the right strategic changes. The result? A remarkable comeback to 695. Check out how Saakshi did it.
Apr 1612:00 PM EDT
-11:59 PM EDT
You’re first to know: Save $200 on GMAT prep starting tomorrow, 4/13. Get 6 official practice tests and study with real questions. Be ready to save!
Apr 2301:30 AM EDT
-02:30 AM EDT
Struggling with GMAT Verbal as a non-native speaker? Harsh improved his score from 595 to 695 in just 45 days—and scored a 99 %ile in Verbal (V88)! Learn how smart strategy, clarity, and guided prep helped him gain 100 points.
Apr 2308:00 PM PDT
-09:00 PM PDT
Video explanations + diagnosis of 10 weakest areas + 150+ short videos + study plan!
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.
16 Sep 2010, 18:22
Kudos
Bookmarks
A
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
25%
(medium)
Question Stats:
75% (01:40) correct
25%
(01:50)
wrong
based on 574
sessions
History
Date
Time
Result
Not Attempted Yet
The integers r and s are distinct, \(r ≠ 0\), and \(s ≠ 0\). If \(r^2s^2 = -rs\), which of the following must be true?
I. r = -1
II. s = 1
III. r - s = 0
A. None
B. I alone
C. II alone
D. III alone
E. I, II and III
I. r = -1
II. s = 1
III. r - s = 0
A. None
B. I alone
C. II alone
D. III alone
E. I, II and III
16 Sep 2010, 18:34
Kudos
Bookmarks
The integers r and s are distinct, \(r ≠ 0\), and \(s ≠ 0\). If \(r^2s^2 = -rs\), which of the following must be true?
I. r = -1
II. s = 1
III. r - s = 0
A. None
B. I alone
C. II alone
D. III alone
E. I, II and III
\(r^2s^2=-rs\) --> as neither of unknowns equal to 0 we can safely reduce this equation by \(rs\) (as \(rs\neq{0}\)) --> \(rs=-1\).
I. r = -1 --> must not be true as \(r\) could be 1 and \(s\) could be -1;
II. s = 1 --> the same here: must not be true as \(r\) could be 1 and \(s\) could be -1;
III. r - s = 0 --> and again the same example works: must not be true as \(r\) could be 1 and \(s\) could be -1 --> \(r-s=1-(-1)=2\neq{0}\) (in fact this statement is never true).
Answer: A (None).
The question asks which of the following MUST be true, or which of the following is ALWAYS true no matter what set of numbers you choose. For such kind of questions if you can prove that a statement is NOT true for one particular set of numbers, it will mean that this statement is not always true and hence not a correct answer.
As for "COULD BE TRUE" questions:
The questions asking which of the following COULD be true are different: if you can prove that a statement is true for one particular set of numbers, it will mean that this statement could be true and hence is a correct answer.
Hope it helps.
I. r = -1
II. s = 1
III. r - s = 0
A. None
B. I alone
C. II alone
D. III alone
E. I, II and III
\(r^2s^2=-rs\) --> as neither of unknowns equal to 0 we can safely reduce this equation by \(rs\) (as \(rs\neq{0}\)) --> \(rs=-1\).
I. r = -1 --> must not be true as \(r\) could be 1 and \(s\) could be -1;
II. s = 1 --> the same here: must not be true as \(r\) could be 1 and \(s\) could be -1;
III. r - s = 0 --> and again the same example works: must not be true as \(r\) could be 1 and \(s\) could be -1 --> \(r-s=1-(-1)=2\neq{0}\) (in fact this statement is never true).
Answer: A (None).
The question asks which of the following MUST be true, or which of the following is ALWAYS true no matter what set of numbers you choose. For such kind of questions if you can prove that a statement is NOT true for one particular set of numbers, it will mean that this statement is not always true and hence not a correct answer.
As for "COULD BE TRUE" questions:
The questions asking which of the following COULD be true are different: if you can prove that a statement is true for one particular set of numbers, it will mean that this statement could be true and hence is a correct answer.
Hope it helps.
gurpreetsingh
Joined: 12 Oct 2009
Last visit: 15 Jun 2019
Posts: 2,266
Given Kudos: 235
Status:<strong>Nothing comes easy: neither do I want.</strong>
Location: Malaysia
Concentration: Technology, Entrepreneurship
Schools: ISB '15 (M)
GMAT 1: 670 Q49 V31
GMAT 2: 710 Q50 V35
Products:
16 Sep 2010, 18:37
Kudos
Bookmarks
ezhilkumarank
Since \(r^2s^2 = -rs\)
=> \(r^2s^2 + rs = 0\),
=> \(rs*(rs+1) = 0\), since it is given that r and s are not equal to 0
=> \(rs+1 = 0\) => \(rs= -1\)
Since r and s are integers, rs =-1 is only possible when one of them is 1 and other -1.
A and B are wrong because either of them could be -1 and 1.
C is wrong because r and s can not be equal because if they are, then rs =-1 can not be true.
Hence answer is I - None
