If the integer n is greater than 1, is n equal to 2?
(1) n has exactly two positive factors
(2) The difference between any two distinct positive factors is odd.
Please provide answer with explanation.
Confusion with wording of option (2) ?
This topic has expert replies
- aneesh.kg
- Master | Next Rank: 500 Posts
- Posts: 385
- Joined: Mon Apr 16, 2012 8:40 am
- Location: Pune, India
- Thanked: 186 times
- Followed by:29 members
If n > 1, is n = 2?
Statement (1): n has exactly two positive factors. So, 'n' can be any prime number. n = 2, 3, 5.. and so on
INSUFFICIENT
Statement (2): The wording of the statement is not clear. If the statement means to say that 'The difference between the only two positive factors of n is an odd integer', then this statement is SUFFICIENT.
This seems like a problem made by a well-meaning amateur.
Statement (1): n has exactly two positive factors. So, 'n' can be any prime number. n = 2, 3, 5.. and so on
INSUFFICIENT
Statement (2): The wording of the statement is not clear. If the statement means to say that 'The difference between the only two positive factors of n is an odd integer', then this statement is SUFFICIENT.
This seems like a problem made by a well-meaning amateur.
Aneesh Bangia
GMAT Math Coach
[email protected]
GMATPad:
Facebook Page: https://www.facebook.com/GMATPad
GMAT Math Coach
[email protected]
GMATPad:
Facebook Page: https://www.facebook.com/GMATPad
- Stuart@KaplanGMAT
- GMAT Instructor
- Posts: 3225
- Joined: Tue Jan 08, 2008 2:40 pm
- Location: Toronto
- Thanked: 1710 times
- Followed by:614 members
- GMAT Score:800
Hi!amp0201 wrote:If the integer n is greater than 1, is n equal to 2?
(1) n has exactly two positive factors
(2) The difference between any two distinct positive factors is odd.
There's nothing ambiguous about (2), it just needs to be read carefully (like all DS statements!).
"The difference between ANY two distinct positive factors of n is odd" must mean two things:
1) n only has 2 distinct factors; and
2) those 2 factors are 1 apart.
The first criterion tells us that n is prime; the second criterion tells us that n=2.
Since the only value that satisfies both of those criteria is 2, statement (2) provides a definite YES answer to the question and is sufficient.
Stuart Kovinsky | Kaplan GMAT Faculty | Toronto
Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
Stuart,
I understand what you are saying. But I assumed n = 6 (distinct factors - 1,2,3,6) and difference between any two distinct factors (6-1) = ODD. Hence n = 2, 6, etc.
So as per your explanation does that mean (2) is looking for ONLY prime numbers, whose factors differ by 1 i.e. difference is odd?
Regards,
Akhil
Aneesh - Thanks for your feedback.
I understand what you are saying. But I assumed n = 6 (distinct factors - 1,2,3,6) and difference between any two distinct factors (6-1) = ODD. Hence n = 2, 6, etc.
So as per your explanation does that mean (2) is looking for ONLY prime numbers, whose factors differ by 1 i.e. difference is odd?
Regards,
Akhil
Aneesh - Thanks for your feedback.
- sanju09
- GMAT Instructor
- Posts: 3650
- Joined: Wed Jan 21, 2009 4:27 am
- Location: India
- Thanked: 267 times
- Followed by:80 members
- GMAT Score:760
I suppose you forgot to consider 6 - 2 = evenamp0201 wrote:Stuart,
I understand what you are saying. But I assumed n = 6 (distinct factors - 1,2,3,6) and difference between any two distinct factors (6-1) = ODD. Hence n = 2, 6, etc.
So as per your explanation does that mean (2) is looking for ONLY prime numbers, whose factors differ by 1 i.e. difference is odd?
Regards,
Akhil
Aneesh - Thanks for your feedback.
The mind is everything. What you think you become. -Lord Buddha
Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001
www.manyagroup.com
Sanjeev K Saxena
Quantitative Instructor
The Princeton Review - Manya Abroad
Lucknow-226001
www.manyagroup.com
- Stuart@KaplanGMAT
- GMAT Instructor
- Posts: 3225
- Joined: Tue Jan 08, 2008 2:40 pm
- Location: Toronto
- Thanked: 1710 times
- Followed by:614 members
- GMAT Score:800
Hi! As Sanju points out, 6-2 is, in fact even; as is 3-1, another pair of factors of 6.amp0201 wrote:Stuart,
I understand what you are saying. But I assumed n = 6 (distinct factors - 1,2,3,6) and difference between any two distinct factors (6-1) = ODD. Hence n = 2, 6, etc.
So as per your explanation does that mean (2) is looking for ONLY prime numbers, whose factors differ by 1 i.e. difference is odd?
Regards,
Akhil
Aneesh - Thanks for your feedback.
Let's think about statement (2) some more. How do we get an odd difference between integers? If one is even and one is odd.
So, if a number has two odd factors, then we'll get an even difference. If a number has two even factors, we'll get an even difference. The only way to guarantee that we'll ALWAYS get an odd difference is if the number has exactly 1 even factor and 1 odd factor - and only 2 fits that bill.
Stuart Kovinsky | Kaplan GMAT Faculty | Toronto
Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
- ronnie1985
- Legendary Member
- Posts: 626
- Joined: Fri Dec 23, 2011 2:50 am
- Location: Ahmedabad
- Thanked: 31 times
- Followed by:10 members
There is ambiguity in the second statement.
Follow your passion, Success as perceived by others shall follow you
- Stuart@KaplanGMAT
- GMAT Instructor
- Posts: 3225
- Joined: Tue Jan 08, 2008 2:40 pm
- Location: Toronto
- Thanked: 1710 times
- Followed by:614 members
- GMAT Score:800
Hi Ronnie,ronnie1985 wrote:There is ambiguity in the second statement.
what, exactly, is ambiguous? I'd argue that there's only one way that it can be properly interpreted (the word "any" is the key to proper interpretation).
Stuart Kovinsky | Kaplan GMAT Faculty | Toronto
Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course
- Stuart@KaplanGMAT
- GMAT Instructor
- Posts: 3225
- Joined: Tue Jan 08, 2008 2:40 pm
- Location: Toronto
- Thanked: 1710 times
- Followed by:614 members
- GMAT Score:800
Hi,PGMAT wrote:I think answer should be (C)
2) says difference is odd but not 1 apart? what if n=12 (1,2,3,4,6,12). 6-3 is odd.
Not sure if I am missing something but C seems to be the right answer.
the key word is "any".
(2) says that the difference between ANY two factors of n is odd; read ANY as EVERY (they mean the same thing).
So, if n=12, then we have lots of pairs of factors that do NOT have an odd difference, e.g.:
3-1=2
4-2=2
6-2=4
and so on...
The only number for which ANY two factors chosen have an odd difference is 2.
Stuart Kovinsky | Kaplan GMAT Faculty | Toronto
Kaplan Exclusive: The Official Test Day Experience | Ready to Take a Free Practice Test? | Kaplan/Beat the GMAT Member Discount
BTG100 for $100 off a full course