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What is the greatest common factor of positive integers x an

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What is the greatest common factor of positive integers x an  [#permalink]

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New post Updated on: 31 Dec 2013, 02:53
7
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

60% (00:52) correct 40% (00:54) wrong based on 373 sessions

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What is the greatest common factor of positive integers x and y?

(1) x and y share only one common factor.
(2) x and y are unique prime numbers.

Below is my solution. Struggling to understand the official answer. Can someone please help?

Considering statement 1 : If X = 6 and Y = 9 then X = 2*3 and Y = 3 *3 and the GCF is 3 which is the common factor shared by both X and Y and of X = 4 and Y = 12 then X = 2^2 and Y = 2^2 * 3. Therefore the GCF is 4. Therefore this statement should be insufficient.

Considering statement 2 : If X = 2 and Y = 3, the GCF is 1 as this is the common factor shared by both.

Hence, I went for B, which is not the case.

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Originally posted by enigma123 on 31 Dec 2013, 01:41.
Last edited by Bunuel on 31 Dec 2013, 02:53, edited 3 times in total.
Renamed the topic and edited the question.
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Re: What is the greatest common factor of positive integers x an  [#permalink]

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New post 31 Dec 2013, 02:55
2
2
enigma123 wrote:
What is the greatest common factor of positive integers x and y?

(1) x and y share only one common factor.
(2) x and y are unique prime numbers.

Below is my solution. Struggling to understand the official answer. Can someone please help?

Considering statement 1 : If X = 6 and Y = 9 then X = 2*3 and Y = 3 *3 and the GCF is 3 which is the common factor shared by both X and Y and of X = 4 and Y = 12 then X = 2^2 and Y = 2^2 * 3. Therefore the GCF is 4. Therefore this statement should be insufficient.

Considering statement 2 : If X = 2 and Y = 3, the GCF is 1 as this is the common factor shared by both.

Hence, I went for B, which is not the case.


What is the greatest common factor of positive integers x and y?

(1) x and y share only one common factor --> every integer has 1 as a factor, thus since x and y share only one common factor it must be 1. Sufficient.

(2) x and y are unique prime numbers. Two different primes can have only 1 as common factor. Sufficient.

Answer: D.

Hope it's clear.
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Re: What is the greatest common factor of positive integers x an  [#permalink]

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New post 18 Feb 2014, 03:33
Let's start with (2). A prime number is only divisible by 1 and itself. Hence the factors of a prime number are only 1 and itself. Now if you have two DIFFERENT unique prime numbers, the factor is 1.

Statement (1). At first I started as you, thought about types of numbers sharing common divisors/factors. Then I remembered that every number is also divisible by 1 and itself. Hence, the numbers mustn't share another factor than one. Hence the GCD would again be 1. Thus D is the correct answer.
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Re: What is the greatest common factor of positive integers x an  [#permalink]

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New post 06 Mar 2014, 04:45
Good question. Stmt 1 points that the common factor is 1 hence (1) is sufficient. Stmt 2 is also sufficient since two primes have 1 as the only common factor. D is the answer.
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Re: What is the greatest common factor of positive integers x an  [#permalink]

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New post 11 Mar 2014, 03:18
Bunuel wrote:
enigma123 wrote:
What is the greatest common factor of positive integers x and y?

(1) x and y share only one common factor.
(2) x and y are unique prime numbers.

Below is my solution. Struggling to understand the official answer. Can someone please help?

Considering statement 1 : If X = 6 and Y = 9 then X = 2*3 and Y = 3 *3 and the GCF is 3 which is the common factor shared by both X and Y and of X = 4 and Y = 12 then X = 2^2 and Y = 2^2 * 3. Therefore the GCF is 4. Therefore this statement should be insufficient.

Considering statement 2 : If X = 2 and Y = 3, the GCF is 1 as this is the common factor shared by both.

Hence, I went for B, which is not the case.


What is the greatest common factor of positive integers x and y?

(1) x and y share only one common factor --> every integer has 1 as a factor, thus since x and y share only one common factor it must be 1. Sufficient.

(2) x and y are unique prime numbers. Two different primes can have only 1 as common factor. Sufficient.

Answer: D.

Hope it's clear.




(BUT) cant the two integers that is x and y be same??
thats y it should be C and not D
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Re: What is the greatest common factor of positive integers x an  [#permalink]

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New post 11 Mar 2014, 03:31
adityavb24 wrote:
Bunuel wrote:
enigma123 wrote:
What is the greatest common factor of positive integers x and y?

(1) x and y share only one common factor.
(2) x and y are unique prime numbers.

Below is my solution. Struggling to understand the official answer. Can someone please help?

Considering statement 1 : If X = 6 and Y = 9 then X = 2*3 and Y = 3 *3 and the GCF is 3 which is the common factor shared by both X and Y and of X = 4 and Y = 12 then X = 2^2 and Y = 2^2 * 3. Therefore the GCF is 4. Therefore this statement should be insufficient.

Considering statement 2 : If X = 2 and Y = 3, the GCF is 1 as this is the common factor shared by both.

Hence, I went for B, which is not the case.


What is the greatest common factor of positive integers x and y?

(1) x and y share only one common factor --> every integer has 1 as a factor, thus since x and y share only one common factor it must be 1. Sufficient.

(2) x and y are unique prime numbers. Two different primes can have only 1 as common factor. Sufficient.

Answer: D.

Hope it's clear.




(BUT) cant the two integers that is x and y be same??
thats y it should be C and not D


For (2) we are given that x and y are distinct: x and y are unique prime numbers.

As for (1): if x and y are the same number, say 3, then they would share all their factors 1 and 3, not just one.

The OA is correct.
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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: What is the greatest common factor of positive integers x an  [#permalink]

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New post 06 Sep 2014, 04:13
enigma123 wrote:
What is the greatest common factor of positive integers x and y?

(1) x and y share only one common factor.
(2) x and y are unique prime numbers.

Below is my solution. Struggling to understand the official answer. Can someone please help?

Considering statement 1 : If X = 6 and Y = 9 then X = 2*3 and Y = 3 *3 and the GCF is 3 which is the common factor shared by both X and Y and of X = 4 and Y = 12 then X = 2^2 and Y = 2^2 * 3. Therefore the GCF is 4. Therefore this statement should be insufficient.

Considering statement 2 : If X = 2 and Y = 3, the GCF is 1 as this is the common factor shared by both.

Hence, I went for B, which is not the case.




1. one is the factor for all the values. since both has only one common factor then it should be one. hence suff.

2. two rpime number shares only one as a common factor. hence suff.

Hence answer D.
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Re: What is the greatest common factor of positive integers x an  [#permalink]

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New post 29 Nov 2016, 04:38
we are not asked to find X and Y, just GCF

St1. Share only one factor means that X and Y are coprime. No matter what number they are (5,6 or 2,3) GCF=1.Suff

St2. X and Y unique primes means again that hey are coprime, so GCF=1.Suff

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Re: What is the greatest common factor of positive integers x an  [#permalink]

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