Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 26 Apr 2015, 13:11

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# If x and n are positive integers , and when (n+1)(n-1) is

Author Message
TAGS:
Manager
Joined: 19 Aug 2006
Posts: 222
Followers: 1

Kudos [?]: 12 [0], given: 0

If x and n are positive integers , and when (n+1)(n-1) is [#permalink]  26 Nov 2006, 22:52
00:00

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
If x and n are positive integers , and when (n+1)(n-1) is divided by 24, the quotient is x and the remainder is r. r=?
1) 2 is not the factor of n
2) 3 is not the factor of n
VP
Joined: 25 Jun 2006
Posts: 1175
Followers: 2

Kudos [?]: 71 [0], given: 0

I got C.

1) means that n is odd. then n + 1 and n - 1 both will be even.
then it has a factor of 2*2 = 4. then we can deduce r is from 1 to 5.

InSuff.

2) means (n+1)(n-1) must have a factor of 3. then r is from 1 to 7.
InSuff.

Both put together, it has a factor or 2*2*3 = 12.
then the remainder can only be 1. C.
VP
Joined: 15 Jul 2004
Posts: 1473
Schools: Wharton (R2 - submitted); HBS (R2 - submitted); IIMA (admitted for 1 year PGPX)
Followers: 17

Kudos [?]: 116 [0], given: 13

Both choices together are sufficient C.

Since n does not have 2 and 3 as factor - it must be a prime number.

Also it must be a prime > 3.

picking primes > 3 we can see that n+1 * n-1 will always be divisible by 24 and hence r = 0.
Manager
Joined: 19 Aug 2006
Posts: 222
Followers: 1

Kudos [?]: 12 [0], given: 0

Thanks for explanation.

OA is C
Similar topics Replies Last post
Similar
Topics:
If x and n are +ve integers and when (n+1)(n-1) is divided 3 23 Sep 2006, 09:06
if n is a +ve intiger and r is the remainder when (n-1)(n+1) 6 07 Sep 2006, 02:58
If n is positive, and r is the remainder when (n-1)(n+1) is 1 26 Apr 2006, 12:21
n is a positive integer. Find the remainder of (n+1)(n-1)/24 9 06 Nov 2005, 12:22
If n is a positive integer, is (n+1)! - (n-1)! greater than 12 12 Jun 2005, 17:21
Display posts from previous: Sort by