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M27-15

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M27-15  [#permalink]

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New post 16 Sep 2014, 00:27
1
10
00:00
A
B
C
D
E

Difficulty:

  75% (hard)

Question Stats:

49% (01:09) correct 51% (01:08) wrong based on 217 sessions

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Re M27-15  [#permalink]

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New post 16 Sep 2014, 00:27
3
1
Official Solution:


Notice that we are not told that \(a\) and \(b\) are positive.

There are the following possible integer pairs of \((a, b)\): (1, 2), (-1, -2), (2, 1) and (-2, -1). Basically, we are asked whether we have the third case.

(1) \(b+3\) is not a prime number. This statement rules out 1st and 4th options. Not sufficient.

(2) \(a \gt b\). This statement also rules out 1st and 4th options. Not sufficient.

(1)+(2) Still two options are left: (-1, -2) and (2, 1). Not sufficient.


Answer: E
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Re: M27-15  [#permalink]

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New post 08 Mar 2018, 14:40
There are the following possible integer pairs of (a,b)(a,b): (1, 2), (-1, -2), (2, 1) and (-2, -1). Basically, we are asked whether we have the third case.

(1) b+3b+3 is not a prime number. This statement rules out 1st and 4th options. Not sufficient.

Yes but, option one also rules out (-1,-2), as 3 + -2 = 1, which is a prime number. It rules out options 1, 2, and 4.
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Re: M27-15  [#permalink]

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New post 27 Sep 2018, 05:00
1
deloitter wrote:
There are the following possible integer pairs of (a,b)(a,b): (1, 2), (-1, -2), (2, 1) and (-2, -1). Basically, we are asked whether we have the third case.

(1) b+3b+3 is not a prime number. This statement rules out 1st and 4th options. Not sufficient.

Yes but, option one also rules out (-1,-2), as 3 + -2 = 1, which is a prime number. It rules out options 1, 2, and 4.


That is not true. Number 1 is not prime
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Re: M27-15  [#permalink]

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New post 28 Sep 2018, 01:58
I did not consider that the numbers could be both negatives. A mistake I need to avoid.
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M27-15  [#permalink]

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New post 27 Oct 2018, 03:45
Bunuel wrote:
Official Solution:


Notice that we are not told that \(a\) and \(b\) are positive.

There are the following possible integer pairs of \((a, b)\): (1, 2), (-1, -2), (2, 1) and (-2, -1). Basically, we are asked whether we have the third case.

(1) \(b+3\) is not a prime number. This statement rules out 1st and 4th options. Not sufficient.

(2) \(a \gt b\). This statement also rules out 1st and 4th options. Not sufficient.

(1)+(2) Still two options are left: (-1, -2) and (2, 1). Not sufficient.


Answer: E



If \(a\) and \(b\) are integers and \(ab=2\), is \(a=2\)?


Question here is whether A is 2 or not??


Considering situation (1) and from your explanation (1, 2) and (-2, -1) can be values.. neither values has a=2, so its clear "a" is not 2, in that case i think its clear that a is not 2 hence, statement 1 is sufficient.

though there are multiple values of a, but we have to answer whether a is 2 or not,, which is clear that it is not under statement 1.


if m wrong pls help me.
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Re: M27-15  [#permalink]

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New post 27 Oct 2018, 04:44
GMAT215 wrote:
Bunuel wrote:
Official Solution:


Notice that we are not told that \(a\) and \(b\) are positive.

There are the following possible integer pairs of \((a, b)\): (1, 2), (-1, -2), (2, 1) and (-2, -1). Basically, we are asked whether we have the third case.

(1) \(b+3\) is not a prime number. This statement rules out 1st and 4th options. Not sufficient.

(2) \(a \gt b\). This statement also rules out 1st and 4th options. Not sufficient.

(1)+(2) Still two options are left: (-1, -2) and (2, 1). Not sufficient.


Answer: E



If \(a\) and \(b\) are integers and \(ab=2\), is \(a=2\)?


Question here is whether A is 2 or not??


Considering situation (1) and from your explanation (1, 2) and (-2, -1) can be values.. neither values has a=2, so its clear "a" is not 2, in that case i think its clear that a is not 2 hence, statement 1 is sufficient.

though there are multiple values of a, but we have to answer whether a is 2 or not,, which is clear that it is not under statement 1.


if m wrong pls help me.


Please re-read.
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Re: M27-15  [#permalink]

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New post 29 Oct 2018, 01:55
Bunuel wrote:
GMAT215 wrote:
Bunuel wrote:
Official Solution:


Notice that we are not told that \(a\) and \(b\) are positive.

There are the following possible integer pairs of \((a, b)\): (1, 2), (-1, -2), (2, 1) and (-2, -1). Basically, we are asked whether we have the third case.

(1) \(b+3\) is not a prime number. This statement rules out 1st and 4th options. Not sufficient.

(2) \(a \gt b\). This statement also rules out 1st and 4th options. Not sufficient.

(1)+(2) Still two options are left: (-1, -2) and (2, 1). Not sufficient.


Answer: E



If \(a\) and \(b\) are integers and \(ab=2\), is \(a=2\)?


Question here is whether A is 2 or not??


Considering situation (1) and from your explanation (1, 2) and (-2, -1) can be values.. neither values has a=2, so its clear "a" is not 2, in that case i think its clear that a is not 2 hence, statement 1 is sufficient.

though there are multiple values of a, but we have to answer whether a is 2 or not,, which is clear that it is not under statement 1.


if m wrong pls help me.


Please re-read.



pls reply..
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Re: M27-15  [#permalink]

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New post 29 Oct 2018, 02:59
Bunuel wrote:
GMAT215 wrote:
Bunuel wrote:
Official Solution:


Notice that we are not told that \(a\) and \(b\) are positive.

There are the following possible integer pairs of \((a, b)\): (1, 2), (-1, -2), (2, 1) and (-2, -1). Basically, we are asked whether we have the third case.

(1) \(b+3\) is not a prime number. This statement rules out 1st and 4th options. Not sufficient.

(2) \(a \gt b\). This statement also rules out 1st and 4th options. Not sufficient.

(1)+(2) Still two options are left: (-1, -2) and (2, 1). Not sufficient.


Answer: E



If \(a\) and \(b\) are integers and \(ab=2\), is \(a=2\)?


Question here is whether A is 2 or not??


Considering situation (1) and from your explanation (1, 2) and (-2, -1) can be values.. neither values has a=2, so its clear "a" is not 2, in that case i think its clear that a is not 2 hence, statement 1 is sufficient.

though there are multiple values of a, but we have to answer whether a is 2 or not,, which is clear that it is not under statement 1.


if m wrong pls help me.


Please re-read.


I think you did not re-read the solution.

The solution clearly says that from statement (1) 1st and 4th options are NOT possible: This statement rules out 1st and 4th options. So, from (1) only (-1, -2) and (2, 1) are possible, NOT (1, 2) and (-2, -1).
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

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. ,11 Mixed Questions, 12 Fresh Meat

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., 11 New DS set.


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Re: M27-15 &nbs [#permalink] 29 Oct 2018, 02:59
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