|
Author |
Message |
|
Founder
Status: On Vacation :-)
Affiliations: UA-1K, SPG-G, HH-D
Joined: 04 Dec 2002
Posts: 10393
Location: United States (WA)
GMAT 1: 750 Q49 V42
GPA: 3.5
WE: Information Technology (Hospitality and Tourism)
Followers: 1355
Kudos [?]:
4175
[3] , given: 3117
|
GMAT Diagnostic Test Question 4 [#permalink]
 06 Jun 2009, 21:06
3
This post received
KUDOS
GMAT Diagnostic Test Question 4Field: Arithmetic, Factorial Difficulty: 650
Is X a prime integer? (1) x! is not divisible by 5 (2) |x|! is divisible by 6 A. Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient B. Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient D. EACH statement ALONE is sufficient E. Statements (1) and (2) TOGETHER are NOT sufficient
_________________
Founder of GMAT Club
Just starting out with GMAT? Start here... | Want to know your GMAT Score? Try GMAT Score Estimator
Need GMAT Book Recommendations? Best GMAT Books
Co-author of the GMAT Club tests
Find out what's new at GMAT Club - latest features and updates
|
|
|
|
|
|
|
|
|
CIO
Joined: 02 Oct 2007
Posts: 1261
Followers: 75
Kudos [?]:
505
[2] , given: 334
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
12 Jun 2009, 07:27
2
This post received
KUDOS
Explanation:
Official Answer: EStatement (1): X<5, i.e X could be 0, 1, 2, 3 or 4 but not 5. Not sufficient. Statement (2): X could be \le -3 or \ge 3. Not sufficient. Statement (1)+Statement (2): X has to be positive. Hence, X can be either 3 or 4. Still insufficient.
_________________
Welcome to GMAT Club! 
   
Want to solve GMAT questions on the go? GMAT Club iPhone app will help.
Please read this before posting in GMAT Club Tests forum
Result correlation between real GMAT and GMAT Club Tests
Are GMAT Club Test sets ordered in any way?
Take 15 free tests with questions from GMAT Club, Knewton, Manhattan GMAT, and Veritas.
Find out what's new at GMAT Club - latest features and updates
|
|
|
|
|
|
Intern
Joined: 01 Jul 2009
Posts: 3
Followers: 0
Kudos [?]:
0
[0], given: 2
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
10 Aug 2009, 19:24
Prime number is a number that can be divided only by itself and the number one. For example, three and seven are prime numbers.
So I think the correct answer is "E".
|
|
|
|
|
|
Manager
Joined: 03 Oct 2009
Posts: 93
Followers: 1
Kudos [?]:
2
[0], given: 2
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
16 Oct 2009, 05:35
why we can't have negative prime numbers? I think we do have -ve prime numbers..
|
|
|
|
|
|
CIO
Joined: 02 Oct 2007
Posts: 1261
Followers: 75
Kudos [?]:
505
[0], given: 334
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
16 Oct 2009, 09:57
I'm afraid GMAC won't agree with you. Prime numbers can't be negative. KocharRohit wrote: why we can't have negative prime numbers? I think we do have -ve prime numbers..
_________________
Welcome to GMAT Club!
Want to solve GMAT questions on the go? GMAT Club iPhone app will help.
Please read this before posting in GMAT Club Tests forum
Result correlation between real GMAT and GMAT Club Tests
Are GMAT Club Test sets ordered in any way?
Take 15 free tests with questions from GMAT Club, Knewton, Manhattan GMAT, and Veritas.
Find out what's new at GMAT Club - latest features and updates
|
|
|
|
|
|
Intern
Joined: 31 Oct 2009
Posts: 2
Followers: 0
Kudos [?]:
0
[0], given: 0
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
08 Nov 2009, 10:46
Statement (2) - Should'nt we consider only the positive value for square root of 4 (and not -2)?
If that is true Stmt 2 would be sufficient, Am I missing something here?
|
|
|
|
|
|
Intern
Joined: 09 Nov 2009
Posts: 1
Schools: Warwick, Manchester, Lancaster, Cass, Imperial
Followers: 0
Kudos [?]:
0
[0], given: 0
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
09 Nov 2009, 04:21
Is X a prime integer?
Statement (1): There are two possible values, +2 & -2
Statement (2): there are 2 possible values +2, -2
Prime number is a number that can be divided only by itself and the number one. For example, three and seven are prime numbers.
So , shouldn't the answer be D cause we get the answer anyway that X is not a prime integer since both the answers are +2 & -2
|
|
|
|
|
|
CIO
Joined: 02 Oct 2007
Posts: 1261
Followers: 75
Kudos [?]:
505
[0], given: 334
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
09 Nov 2009, 04:24
This is one of the common misunderstandings. If the question asked for the value of \sqrt{4}, then it would surely be 2 and not -2 on GMAT. However, when it is stated that X^2=4, you have two options, 2 and -2. There's nothing wrong in squaring a negative number. Does this explanation make any sense? kl wrote: Statement (2) - Should'nt we consider only the positive value for square root of 4 (and not -2)?
If that is true Stmt 2 would be sufficient, Am I missing something here?
_________________
Welcome to GMAT Club!
Want to solve GMAT questions on the go? GMAT Club iPhone app will help.
Please read this before posting in GMAT Club Tests forum
Result correlation between real GMAT and GMAT Club Tests
Are GMAT Club Test sets ordered in any way?
Take 15 free tests with questions from GMAT Club, Knewton, Manhattan GMAT, and Veritas.
Find out what's new at GMAT Club - latest features and updates
|
|
|
|
|
|
CIO
Joined: 02 Oct 2007
Posts: 1261
Followers: 75
Kudos [?]:
505
[0], given: 334
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
09 Nov 2009, 04:27
+2 is a prime, -2 is not. Combining the two statements still doesn't give us more information. We can't be certain if X is prime (2) or not (-2) as both values of X are possible. pdew wrote: Is X a prime integer?
Statement (1): There are two possible values, +2 & -2
Statement (2): there are 2 possible values +2, -2
Prime number is a number that can be divided only by itself and the number one. For example, three and seven are prime numbers.
So , shouldn't the answer be D cause we get the answer anyway that X is not a prime integer since both the answers are +2 & -2
_________________
Welcome to GMAT Club!
Want to solve GMAT questions on the go? GMAT Club iPhone app will help.
Please read this before posting in GMAT Club Tests forum
Result correlation between real GMAT and GMAT Club Tests
Are GMAT Club Test sets ordered in any way?
Take 15 free tests with questions from GMAT Club, Knewton, Manhattan GMAT, and Veritas.
Find out what's new at GMAT Club - latest features and updates
|
|
|
|
|
|
Manager
Joined: 24 Jul 2009
Posts: 197
Location: Anchorage, AK
Schools: Mellon, USC, MIT, UCLA, NSCU
Followers: 4
Kudos [?]:
17
[0], given: 10
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
26 Nov 2009, 08:09
seemed so simple...thanks for the question and the lesson learned story for the water cooler next week: "What'd ya do Thanksgiving?" response: "Learned that -2 is not prime." 
_________________
Reward wisdom with kudos. 
|
|
|
|
|
|
Intern
Joined: 24 Jan 2010
Posts: 5
Followers: 0
Kudos [?]:
0
[0], given: 0
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
24 Jan 2010, 10:06
This question tricked me.
Actually i though |X| is only positive integer.
|
|
|
|
|
|
GMAT Club team member
Joined: 02 Sep 2009
Posts: 11515
Followers: 1791
Kudos [?]:
9536
[0], given: 826
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
24 Jan 2010, 10:24
|
|
|
|
|
|
Intern
Joined: 31 Aug 2009
Posts: 17
Schools: University of Warwick
Followers: 0
Kudos [?]:
18
[0], given: 3
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
16 Feb 2010, 07:45
Bunuel wrote: beautifullLif3 wrote: This question tricked me.
Actually i though |X| is only positive integer. Absolute value, |x| in our case, is never negative, |some expression|>=0. But the expression IN it (in ||) can be negative. So |x| >=0, but x can take ANY value, positive, zero, negative. We are asked whether x is a prime number not absolute value of x (not |x|). One more thing regarding this question: prime numbers are ONLY positive. 3 is prime, while -3 is not. Hope it helps. since we're on the subject of prime numbers, one more addition to this would be that prime numbers are always odd. thus it becomes positive odd numbers, which can be divided by itself and 1 is it right that we go about handing absolute equations like this: for e.g. if we have |(any expression)| = 4 then that expression could mean either of these: (any expression) = 4 OR (any expression) = -4 we take one positive value of the number on the right hand side and one negative value? is my understanding correct about absolute values?
|
|
|
|
|
|
GMAT Club team member
Joined: 02 Sep 2009
Posts: 11515
Followers: 1791
Kudos [?]:
9536
[0], given: 826
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
16 Feb 2010, 08:03
meganbaxter1 wrote: Bunuel wrote: beautifullLif3 wrote: This question tricked me.
Actually i though |X| is only positive integer. Absolute value, |x| in our case, is never negative, |some expression|>=0. But the expression IN it (in ||) can be negative. So |x| >=0, but x can take ANY value, positive, zero, negative. We are asked whether x is a prime number not absolute value of x (not |x|). One more thing regarding this question: prime numbers are ONLY positive. 3 is prime, while -3 is not. Hope it helps. since we're on the subject of prime numbers, one more addition to this would be that prime numbers are always odd.thus it becomes positive odd numbers, which can be divided by itself and 1 is it right that we go about handing absolute equations like this: for e.g. if we have |(any expression)| = 4 then that expression could mean either of these: (any expression) = 4 OR (any expression) = -4 we take one positive value of the number on the right hand side and one negative value? is my understanding correct about absolute values? Red part is not correct: 2 is even and is prime, it's also the only even prime and the smallest prime. About the absolute value you are correct. I'd suggest to check "Absolute value" and "Number theory" chapters in Math Book and also the topic "Inequalities" (links in my signature).
_________________
PLEASE READ AND FOLLOW: 11 Rules for Posting!!!
RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory
COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. NEW!!!
DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set. NEW!!!
What are GMAT Club Tests?
25 extra-hard Quant Tests
Find out what's new at GMAT Club - latest features and updates
|
|
|
|
|
|
Director
Joined: 21 Dec 2009
Posts: 592
Concentration: Entrepreneurship, Finance
Followers: 13
Kudos [?]:
130
[0], given: 20
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
02 Apr 2010, 05:15
Missed this because I assumed (wrongly) that -x can be a prime number. However, can we also have -x! -negative factorials. for example: (-4)! is it -4*-3.....*2*1?
_________________
KUDOS me if you feel my contribution has helped you.
|
|
|
|
|
|
CIO
Joined: 02 Oct 2007
Posts: 1261
Followers: 75
Kudos [?]:
505
[0], given: 334
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
02 Apr 2010, 05:40
Factorials of negative numbers are undefined on the GMAT. You won't encounter a negative number followed by a factorial sign on the GMAT. gmatbull wrote: Missed this because I assumed (wrongly) that -x can be a prime number.
However, can we also have -x! -negative factorials.
for example: (-4)! is it -4*-3.....*2*1?
_________________
Welcome to GMAT Club!
Want to solve GMAT questions on the go? GMAT Club iPhone app will help.
Please read this before posting in GMAT Club Tests forum
Result correlation between real GMAT and GMAT Club Tests
Are GMAT Club Test sets ordered in any way?
Take 15 free tests with questions from GMAT Club, Knewton, Manhattan GMAT, and Veritas.
Find out what's new at GMAT Club - latest features and updates
|
|
|
|
|
|
Director
Joined: 21 Dec 2009
Posts: 592
Concentration: Entrepreneurship, Finance
Followers: 13
Kudos [?]:
130
[1] , given: 20
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
02 Apr 2010, 05:56
1
This post received
KUDOS
dzyubam wrote: Factorials of negative numbers are undefined on the GMAT. You won't encounter a negative number followed by a factorial sign on the GMAT. gmatbull wrote: Missed this because I assumed (wrongly) that -x can be a prime number.
However, can we also have -x! -negative factorials.
for example: (-4)! is it -4*-3.....*2*1? It was such a dummy question anyway. from the basic explanation: 2! = 3!/3 = 2 1! = 2!/2 = 1 0! = 1!/1 = 1 -1! = 0!/0 => undefined similarly, for all negative numbers: (-x)! is undefined.
_________________
KUDOS me if you feel my contribution has helped you.
|
|
|
|
|
|
Manager
Joined: 05 Mar 2010
Posts: 220
Followers: 1
Kudos [?]:
14
[0], given: 8
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
06 Apr 2010, 06:41
If we take x = 3 or 4 then it satisfies both stmt 1 and stmt 2 but we still dont know whether x is prime or not. because 3 is prime but 4 is not Am i missing something 
_________________
Success is my Destiny
|
|
|
|
|
|
Manager
Joined: 05 Mar 2010
Posts: 220
Followers: 1
Kudos [?]:
14
[1] , given: 8
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
08 Apr 2010, 03:00
1
This post received
KUDOS
Bunuel wrote: beautifullLif3 wrote: This question tricked me.
Actually i though |X| is only positive integer. Absolute value, |x| in our case, is never negative, |some expression|>=0. But the expression IN it (in ||) can be negative. So |x| >=0, but x can take ANY value, positive, zero, negative. We are asked whether x is a prime number not absolute value of x (not |x|). One more thing regarding this question: prime numbers are ONLY positive. 3 is prime, while -3 is not. Hope it helps. Bunuel Please clear my doubt here Stmt 1 say that x can be 0,1,2,3,4 stmt 2 says -3>= x =>3 Both insufficient to make conclusion Stmt 1 +Stmt 2 = x can be 3 or 4. Hence not sufficient Please explain if i am wrong or missing something here?????
_________________
Success is my Destiny
|
|
|
|
|
|
GMAT Club team member
Joined: 02 Sep 2009
Posts: 11515
Followers: 1791
Kudos [?]:
9536
[2] , given: 826
|
Re: GMAT Diagnostic Test Question 4 [#permalink]
08 Apr 2010, 03:20
2
This post received
KUDOS
|
|
|
|
|
|
|
Re: GMAT Diagnostic Test Question 4
[#permalink]
08 Apr 2010, 03:20
|
|
|
|
|
|
|
|
|
|
|
close
