Events & Promotions
|
|
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
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Mar 2911:30 AM EDT
-12:30 PM EDT
Learn how Keshav, a Chartered Accountant, scored an impressive 705 on GMAT in just 30 days with GMATWhiz's expert guidance. In this video, he shares preparation tips and strategies that worked for him, including the mock, time management, and more.
Mar 3005:30 AM PDT
-07:30 AM PDT
We know Strengthen and Weaken questions account for more than 50% of the CR questions on the GMAT. With CR becoming even more important on GMAT Focus, it's time you strengthen your weaknesses with an approach that improves your solving time and accuracy!
Mar 3011:00 AM IST
-01:00 PM IST
Attend this session to evaluate your current skill level, learn process skills, and solve through tough Arithmetic questions.
Mar 3110:00 AM EDT
-11:59 PM EDT
The Target Test Prep team has recently introduced TTP OnDemand GMAT, a 400-hour live masterclass video course created by Scott Woodbury-Stewart, founder and CEO of Target Test Prep.
Apr 0308:00 PM PDT
-09:00 PM PDT
Full-length FE mock with insightful analytics, weakness diagnosis, and video explanations!
gurpreetsingh
Joined: 12 Oct 2009
Last visit: 15 Jun 2019
Posts: 2,276
Given Kudos: 235
Status:<strong>Nothing comes easy: neither do I want.</strong>
Location: Malaysia
Concentration: Technology, Entrepreneurship
Schools: ISB '15 (M)
GMAT 1: 670 Q49 V31
GMAT 2: 710 Q50 V35
Products:
Updated on: 14 Sep 2014, 17:29
Originally posted by gurpreetsingh on 21 Oct 2010, 17:01.
Last edited by Bunuel on 14 Sep 2014, 17:29, edited 1 time in total.
Last edited by Bunuel on 14 Sep 2014, 17:29, edited 1 time in total.
Edited the question and added the OA.
Kudos
Bookmarks
D
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
95%
(hard)
Question Stats:
51% (02:35) correct
49%
(02:25)
wrong
based on 1635
sessions
History
Date
Time
Result
Not Attempted Yet
Is the two digit positive integer P a prime number?
(1) P + 2 and P – 2 are prime.
(2) P – 4 and P + 4 are prime.
(1) P + 2 and P – 2 are prime.
(2) P – 4 and P + 4 are prime.
21 Oct 2010, 17:52
Kudos
Bookmarks
gurpreetsingh
Is the two digit positive integer P a prime number?
1) P + 2 and P – 2 are prime.
2) P – 4 and P + 4 are prime.
I will post the solution and the explanation later.
1) P + 2 and P – 2 are prime.
2) P – 4 and P + 4 are prime.
I will post the solution and the explanation later.
Good question, +1.
Note that P is the two digit integer .
(1) P + 2 and P – 2 are prime --> out of every 3 consecutive integers one must be divisible by 3 --> consider 5 consecutive integers: {P-2}{P-1}{P}{P+1}{P+2}. Now, P-2 and P+2 are not divisible by 3 as they are primes, P+1 and P-1 are 3 apart from P-2 and P+2 respectively and thus they are also not divisible by 3, which means that P must be divisible by 3 and as it's TWO digit integer it cannot be a prime. Sufficient.
(2) P – 4 and P + 4 are prime --> the same here: {P-1}{P}{P+1}. P-1 and P+1 are 3 apart from P-4 and P+4 respectively and thus cannot be divisible by 3, which means that P must be divisible by 3 and as it's TWO digit integer it cannot be a prime. Sufficient.
Answer: D.
12 Jul 2018, 00:30
Kudos
Bookmarks
gurpreetsingh
Is the two digit positive integer P a prime number?
(1) P + 2 and P – 2 are prime.
(2) P – 4 and P + 4 are prime.
(1) P + 2 and P – 2 are prime.
(2) P – 4 and P + 4 are prime.
all 2 digit primes are either of the form 6k+1 or 6k-1 (actually all primes except 2 & 3 are of that form)
statement 1) p+2 & p-2 are prime
if p is prime of the form 6k+1
then p+2 is of form 6k+3 which can not be a prime so p is not a prime of form 6k+1
if p is prime of the form 6k-1
then p-2 is of the form 6k-3 which cannot be a prime so p is not a prime of form 6k-1
hence, p is not a prime. sufficient.
statement 2) p+4 & p-4 are prime
if p is prime of the form 6k+1
then p+4 is of the form 6k+5 which cannot be prime so p is not a prime of form 6k+1
if p is prime of the form 6k-1
then p+4 is of the form 6k+3 which cannot be prime so p is not a prime of form 6k-1
hence, p is not a prime. sufficient.
D.
) 
