Last visit was: 30 Apr 2026, 20:34 It is currently 30 Apr 2026, 20:34
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
chetan2u
User avatar
GMAT Expert
Joined: 02 Aug 2009
Last visit: 30 Apr 2026
Posts: 11,236
Own Kudos:
45,055
 [3]
Given Kudos: 335
Status:Math and DI Expert
Location: India
Concentration: Human Resources, General Management
GMAT Focus 1: 735 Q90 V89 DI81
Products:
Expert
Expert reply
GMAT Focus 1: 735 Q90 V89 DI81
Posts: 11,236
Kudos: 45,055
 [3]
1
Kudos
Add Kudos
2
Bookmarks
Bookmark this Post
User avatar
HKD1710
User avatar
Retired Moderator
Joined: 22 Jun 2014
Last visit: 26 Feb 2021
Posts: 958
Own Kudos:
Given Kudos: 182
Location: India
Concentration: General Management, Technology
GMAT 1: 540 Q45 V20
GPA: 2.49
WE:Information Technology (Computer Software)
GMAT 1: 540 Q45 V20
Posts: 958
Kudos: 4,668
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
Kurtosis
User avatar
Current Student
Joined: 13 Apr 2015
Last visit: 10 Nov 2021
Posts: 1,384
Own Kudos:
5,239
 [1]
Given Kudos: 1,228
Location: India
Products:
Posts: 1,384
Kudos: 5,239
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
chetan2u
User avatar
GMAT Expert
Joined: 02 Aug 2009
Last visit: 30 Apr 2026
Posts: 11,236
Own Kudos:
45,055
 [1]
Given Kudos: 335
Status:Math and DI Expert
Location: India
Concentration: Human Resources, General Management
GMAT Focus 1: 735 Q90 V89 DI81
Products:
Expert
Expert reply
GMAT Focus 1: 735 Q90 V89 DI81
Posts: 11,236
Kudos: 45,055
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Vyshak
chetan2u
If x = n!+1, is x a prime number?
(1) x has no factor other than 1 common with any number less than or equal to n.
(2) x has no factor other than 1 common with any integer greater than n.


self made
OA in 2 days

Hi Chetan,

I am a bit skeptical about Statement 2.

St2: x has no factor other than 1 common with any integer greater than n:
n = 0 --> x = 2 but x cannot be 2 because x has a factor common with 2 which is > 0
n = 2 --> x = 3 but x cannot be 3 because x has a factor common with 3 which is > 2
n = 5 --> x = 121 but x cannot be 121 because x has a factor common with 11 which is > 5
Actually this statement states that x can be 0, 1 or any negative integer. However, according to the given expression, minimum value of x has to be 2.

Statement 2 appears to be flawed. Please correct me if I am wrong.

thanks there was something missed out...
(2) x has no factor other than 1 common with any integer greater than n and lesser than or equal to n!
I have changed the statement
User avatar
chetan2u
User avatar
GMAT Expert
Joined: 02 Aug 2009
Last visit: 30 Apr 2026
Posts: 11,236
Own Kudos:
45,055
 [1]
Given Kudos: 335
Status:Math and DI Expert
Location: India
Concentration: Human Resources, General Management
GMAT Focus 1: 735 Q90 V89 DI81
Products:
Expert
Expert reply
GMAT Focus 1: 735 Q90 V89 DI81
Posts: 11,236
Kudos: 45,055
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
chetan2u
If x = n!+1, is x a prime number?
(1) x has no factor other than 1 common with any number less than or equal to n.
(2) x has no factor other than 1 common with any integer between n and n! , inclusive.


self made
OA in 2 days

x = n!+1...
Now n! is a multiple of all integers till n, so n!+1 will be co-prime to each integer till n..
BUT we require to know if x has any common factor other than 1 with integers from n to n!


lets see the statements


(1) x has no factor other than 1 common with any number less than or equal to n.
No NEW info..
as can be seen x is co-prime with all integers till n, inclusive
so insuff

(2) x has no factor other than 1 common with any integer between n and n! , inclusive.
this says that all integers between n and n!, inclusive are co-prime to x..
we already know as x=n!+1 that x is co-prime to all integers till n, inclusive..
so x does not have any integer less than itself that has any other factor except 1 common with x..
Suff

B

example-
3! + 1 = 7.. satisfies the statement II and thus is PRIME..
On other hand -
\(4! + 1 =25..\)
now x is co-prime with all integers till 4, BUT not from 4 to 24, as it has common factors with 5,10,15,and 20.. hence does not follow statement II and is not a PRIME..
User avatar
Kurtosis
User avatar
Current Student
Joined: 13 Apr 2015
Last visit: 10 Nov 2021
Posts: 1,384
Own Kudos:
Given Kudos: 1,228
Location: India
Products:
Posts: 1,384
Kudos: 5,239
Kudos
Add Kudos
Bookmarks
Bookmark this Post
x = n! + 1

St1: x has no factor other than 1 common with any number less than or equal to n:
n = 2; x = 3 --> 3 is prime
n = 4; x = 25 --> 25 has no common factors between 2 and 4. 25 is not prime
Not Sufficient

St2: x has no factor other than 1 common with any integer between n and n! , inclusive.
n = 0; x = 2 --> Prime
n = 1; x = 2 --> Prime
n = 2; x = 3 --> Prime
n = 3; x = 7 --> Prime
n = 4; x = 25 --> Not a valid value as x has a factor 5
n = 5; x = 121 --> Not a valid value as x has a factor 11
As we can see if x is not prime it will have some factor between n and n! and that value cannot be considered valid.
Sufficient

Answer: B
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 39,011
Own Kudos:
Posts: 39,011
Kudos: 1,122
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
110017 posts
498 posts
212 posts