Last visit was: 24 Apr 2026, 08:11 It is currently 24 Apr 2026, 08:11
Close
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

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Close
Request Expert Reply
Confirm Cancel
User avatar
Mo2men
Joined: 26 Mar 2013
Last visit: 09 May 2023
Posts: 2,426
Own Kudos:
1,508
 [43]
Given Kudos: 641
Concentration: Operations, Strategy
Schools: Erasmus (II)
Products:
Schools: Erasmus (II)
Posts: 2,426
Kudos: 1,508
 [43]
3
Kudos
Add Kudos
40
Bookmarks
Bookmark this Post
Most Helpful Reply
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 24 Apr 2026
Posts: 109,814
Own Kudos:
Given Kudos: 105,871
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 109,814
Kudos: 811,014
 [16]
7
Kudos
Add Kudos
9
Bookmarks
Bookmark this Post
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 24 Apr 2026
Posts: 109,814
Own Kudos:
811,014
 [6]
Given Kudos: 105,871
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 109,814
Kudos: 811,014
 [6]
Kudos
Add Kudos
5
Bookmarks
Bookmark this Post
General Discussion
avatar
hargun3045
Joined: 06 Feb 2018
Last visit: 29 Nov 2022
Posts: 16
Own Kudos:
Given Kudos: 5
Posts: 16
Kudos: 4
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Hi Bunuel
I often struggle with such questions. What topic should I revisit to get better on such questions?
User avatar
LoneSurvivor
Joined: 23 Nov 2016
Last visit: 18 Jul 2021
Posts: 294
Own Kudos:
Given Kudos: 156
GMAT 1: 690 Q50 V33
Products:
GMAT 1: 690 Q50 V33
Posts: 294
Kudos: 774
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
If n is a positive integer, what is the greatest common factor of n and 64?

Notice that 64 = 2^6. So, the GCF of n and 2^6 is either 1 or some power of 2 (from 2 to 2^6).

(1) No two different factors of n sum to a prime number. This implies that 2 is NOT a factor of n, if it were then the sum of two factors of n, 1 and 2, would be a prime number. Since 2 is not a factor of n, then the GCF of n and 2^6 is 1. Sufficient.

(2) The greatest common factor of n and 2,310 is 165. So, the GCF of n and some even number is NOT even. This implies that 2 is NOT a factor of n. Since 2 is not a factor of n, then the GCF of n and 2^6 is 1. Sufficient.

Answer: D.

Hope it's clear.

Hi Bunuel what if the n is in the form of 2^p where none of the two factors of 2^p will add to a prime number. but we do not know what is the value of P so we certainly can not determine GCF .So statement 1 is not sufficient.
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 24 Apr 2026
Posts: 109,814
Own Kudos:
Given Kudos: 105,871
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 109,814
Kudos: 811,014
Kudos
Add Kudos
Bookmarks
Bookmark this Post
LoneSurvivor
Bunuel
If n is a positive integer, what is the greatest common factor of n and 64?

Notice that 64 = 2^6. So, the GCF of n and 2^6 is either 1 or some power of 2 (from 2 to 2^6).

(1) No two different factors of n sum to a prime number. This implies that 2 is NOT a factor of n, if it were then the sum of two factors of n, 1 and 2, would be a prime number. Since 2 is not a factor of n, then the GCF of n and 2^6 is 1. Sufficient.

(2) The greatest common factor of n and 2,310 is 165. So, the GCF of n and some even number is NOT even. This implies that 2 is NOT a factor of n. Since 2 is not a factor of n, then the GCF of n and 2^6 is 1. Sufficient.

Answer: D.

Hope it's clear.

Hi Bunuel what if the n is in the form of 2^p where none of the two factors of 2^p will add to a prime number. but we do not know what is the value of P so we certainly can not determine GCF .So statement 1 is not sufficient.

2^p is 2, 4, 8, ... For any of these values you can pick 1 and 2 as factors, which gives the sum of 3, which is a prime.
avatar
vipulshahi
Joined: 24 Sep 2013
Last visit: 30 Aug 2021
Posts: 163
Own Kudos:
113
 [1]
Given Kudos: 40
Location: Saudi Arabia
GPA: 3.8
WE:Project Management (Energy)
Posts: 163
Kudos: 113
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Dear Bunuel,

Can you elaborate more about the line

(1) No two different factors of n sum to a prime number. This implies that 2 is NOT a factor of n, if it were then the sum of two factors of n, 1 and 2, would be a prime number.
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 24 Apr 2026
Posts: 109,814
Own Kudos:
Given Kudos: 105,871
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 109,814
Kudos: 811,014
Kudos
Add Kudos
Bookmarks
Bookmark this Post
vipulshahi
Dear Bunuel,

Can you elaborate more about the line

(1) No two different factors of n sum to a prime number. This implies that 2 is NOT a factor of n, if it were then the sum of two factors of n, 1 and 2, would be a prime number.

Any even number has at least the following factors: 1 and 2. The sum = 3 = prime.

(1) says that "No two different factors of n sum to a prime number". So, n is NOT even.
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Quote:
If n is a positive integer, what is the greatest common factor of n and 64?

(1) No two different factors of n sum to a prime number.

(2) The greatest common factor of n and 2,310 is 165.

OFFICIAL EXPLANATION:

(1) SUFFICIENT: Every number has 1 as a factor. If n were an even integer, then 1 and 2 would both be factors of n. The sum of 1 and 2 is 3, though, which is prime. Therefore, because 1 has to be a factor, 2 cannot also be a factor. Therefore, n is odd, as are all factors of n (since an odd number can’t have an even factor).
The prime factorization of 64 is 2 , so 64 has no odd factors other than 1.
All factors of n are odd, and all factors of 64 are even except 1. The greatest common factor of n and 64 is therefore 1. The statement is sufficient.

(2) SUFFICIENT: 2,310 is an even integer. If n were an even integer, then the greatest common factor of n and 2,310 would be even (since n and 2,310 would have at least the factor 2 in common). Since the greatest common factor, 165, is odd, it follows that n cannot be even.
If you’re not sure about that, prove it to yourself. Break 2,310 and 165 into their prime factors:
2,310: 2, 3, 5, 7, 11
165: 3, 5, 11
Since 165 is the greatest common factor, n can’t contain a 2 or a 7. Therefore, n is not even.
Thus all factors of n are odd, and, as mentioned above, all factors of 64 are even except 1. The greatest common factor of n and 64 is therefore 1. The statement is sufficient.
The correct answer is (D).
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 38,972
Own Kudos:
Posts: 38,972
Kudos: 1,117
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Automated notice from GMAT Club BumpBot:

A member just gave Kudos to this thread, showing it’s still useful. I’ve bumped it to the top so more people can benefit. Feel free to add your own questions or solutions.

This post was generated automatically.
Moderators:
Math Expert
109814 posts
498 posts
212 posts