It is currently 16 Dec 2017, 16:45

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

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If u and v are distinct prime numbers, which of the following CANNOT b

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

VP
VP
User avatar
V
Status: Preparing for the GMAT
Joined: 02 Nov 2016
Posts: 1306

Kudos [?]: 1141 [0], given: 547

Location: Pakistan
GPA: 3.4
Premium Member
If u and v are distinct prime numbers, which of the following CANNOT b [#permalink]

Show Tags

New post 15 Apr 2017, 08:06
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

57% (01:11) correct 43% (01:41) wrong based on 42 sessions

HideShow timer Statistics

If u and v are distinct prime numbers, which of the following CANNOT be a prime number?

A. uv + 3v − 2
B. uv – u + 2v − 2
C. uv + 2u – v − 2
D. uv + 3u − 2v − 6
E. uv + u + v + 1
[Reveal] Spoiler: OA

_________________

Official PS Practice Questions
Press +1 Kudos if this post is helpful

Kudos [?]: 1141 [0], given: 547

Manager
Manager
avatar
S
Joined: 05 Nov 2016
Posts: 89

Kudos [?]: 21 [0], given: 16

GMAT ToolKit User
Re: If u and v are distinct prime numbers, which of the following CANNOT b [#permalink]

Show Tags

New post 16 Apr 2017, 10:55
Sum of two odd numbers is even and product of two odd numbers is odd.(for prime numbers other than 2)

Sum of one even and one odd is odd and product of one even and one odd is even.(for prime no. 2)

Going by this logic, the last option always gives us the even number as it is added by one. (odd +1 = even)
_________________

Kudos are always welcome ... as well your suggestions

Kudos [?]: 21 [0], given: 16

Expert Post
Top Contributor
2 KUDOS received
SVP
SVP
User avatar
G
Joined: 11 Sep 2015
Posts: 1913

Kudos [?]: 2764 [2], given: 364

Location: Canada
Re: If u and v are distinct prime numbers, which of the following CANNOT b [#permalink]

Show Tags

New post 16 Apr 2017, 12:26
2
This post received
KUDOS
Expert's post
Top Contributor
SajjadAhmad wrote:
If u and v are distinct prime numbers, which of the following CANNOT be a prime number?

A. uv + 3v − 2
B. uv – u + 2v − 2
C. uv + 2u – v − 2
D. uv + 3u − 2v − 6
E. uv + u + v + 1


NOTE: this is one of those questions that require us to check/test each answer choice. In these situations, always check the answer choices from E to A, because the correct answer is typically closer to the bottom than to the top.

For more on this strategy, see my article: http://www.gmatprepnow.com/articles/han ... -questions

E. uv + u + v + 1
Notice that we can factor this expression IN PARTS.
We get: uv + u + v + 1 = u(v + 1) + 1(v + 1)
= (u + 1)(v + 1)
Since we are adding 1 to u and adding 1 to v, we know that (u+1) does not equal 1, and (v+1) does not equal 1
So, we can be CERTAIN that (u + 1)(v + 1) is a COMPOSITE number, which means it is NOT PRIME.

Answer:
[Reveal] Spoiler:
E


Cheers,
Brent
_________________

Brent Hanneson – Founder of gmatprepnow.com

Image

Kudos [?]: 2764 [2], given: 364

Expert Post
1 KUDOS received
e-GMAT Representative
User avatar
S
Joined: 04 Jan 2015
Posts: 755

Kudos [?]: 2244 [1], given: 123

Re: If u and v are distinct prime numbers, which of the following CANNOT b [#permalink]

Show Tags

New post 16 Apr 2017, 21:01
1
This post received
KUDOS
Expert's post
SajjadAhmad wrote:
If u and v are distinct prime numbers, which of the following CANNOT be a prime number?

A. uv + 3v − 2
B. uv – u + 2v − 2
C. uv + 2u – v − 2
D. uv + 3u − 2v − 6
E. uv + u + v + 1


    A. uv + 3v – 2 = v(u+3) – 2
      • Could be prime, v= 3 and u = 2
    B. uv – u + 2v – 2 = (u+2)(v-1)
      • Could be prime, v= 2 and u = 3
    C. uv + 2u – v – 2 = (u-1)(v+2)
      • Could be prime, u = 2 and v =3
    D. uv + 3u − 2v – 6 = (u-2) (v+3)
      • Could be prime, u = 3 and v = 2
    E. uv + u + v + 1 = (v+1) (u+ 1) = cannot be prime,
      • v+1 and u + 1 both simultaneously cannot be prime. If v= 2, v+1 = 3 is prime, they are only consecutive prime number. As v and u are distinct, u + 1 will never be prime and hence expression E can never be prime.

Thanks,
Saquib
Quant Expert
e-GMAT

Register for our Free Session on Number Properties (held every 3rd week) to solve exciting 700+ Level Questions in a classroom environment under the real-time guidance of our Experts :)

Image
_________________












| '4 out of Top 5' Instructors on gmatclub | 70 point improvement guarantee | www.e-gmat.com

Kudos [?]: 2244 [1], given: 123

Re: If u and v are distinct prime numbers, which of the following CANNOT b   [#permalink] 16 Apr 2017, 21:01
Display posts from previous: Sort by

If u and v are distinct prime numbers, which of the following CANNOT b

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


cron

GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.