BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem
TTP OnDemand GMAT Video Course
Featured Course

Target Test Prep GMAT OnDemand

Scott Woodbury-Stewart’s private virtual classroom — 400 hours of master-class video lessons for the GMAT Focus Edition.

  • 715+ score guarantee — highest in the industry (99th percentile)
  • 52 chapters · 1,500+ lessons · 4,000+ practice questions
  • 400 hours of video · 1,500+ instructor-led HD smartboard lessons
  • 300,000+ students accepted to Harvard, Stanford, Wharton, Booth & Sloan & more
  • 24/7 live support + weekly Zoom office hours with GMAT instructors
  • TTP AI Assist — 24/7 AI-powered virtual tutor for instant help
  • 1,200+ flashcards + AI-powered study assistant & daily calendar
  • OnDemand, LiveTeach & GMAT Bootcamp formats available
  • Also: GRE, SAT Math & Executive Assessment courses
  • MBA Admissions Consulting now available
  • 🏆 2025 EdTech Breakthrough Award: Test Prep Solution Provider of the Year
  • 200,000+ students served
  • 5-day free trial — $0 to start, no auto-billing, cancel anytime
★★★★★ 5.0 (559 reviews)
130-pt guarantee
$0 to start then $127/mo
Start Free 5-Day Trial Read 559 Reviews →

Composite primes

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Data Sufficiency |
Legendary Member
Posts: 2467
Joined: Thu Aug 28, 2008 6:14 pmFollowed by: 11 members
Thanked: 331 times

by cramya » Sun Dec 07, 2008 12:47 pm
Take the easier of the 2 statements:

Stmt II

2 digit number greater than 20 with tens digit 2


23 - not composite
24 - composite

INSUFF

Stmt I

Numbers

22,24,26,28,30,33,36,39,40,,44,48,50,55,60,66,70,77,80,88,90,99

All of these are composite

SUFF

A)

Other than listing the numbers which can be done within 2 minutes I coudnt think of a shorcut
Last edited by cramya on Sun Dec 07, 2008 12:50 pm, edited 1 time in total.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Legendary Member
Posts: 2134
Joined: Mon Oct 20, 2008 11:26 pmFollowed by: 25 members
Thanked: 237 times
GMAT Score:730

by logitech » Sun Dec 07, 2008 12:49 pm
cramya wrote: Other than listing the numbers which can be done within 2 minutes I coudnt think of a shorcut
You don't need a shortcut here bro. Good thinking , clean solution! Sweet!
LGTCH
---------------------
"DON'T LET ANYONE STEAL YOUR DREAM!"
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 2467
Joined: Thu Aug 28, 2008 6:14 pmFollowed by: 11 members
Thanked: 331 times

by cramya » Sun Dec 07, 2008 12:51 pm
Keep in mind the following:

1) 0 is a multiple of every number
2) 1 is a factor of every number
3) 0 has infinetely many factors (thats why I added 30,40,50,60,... to the list above since the tens digit in each number is a factor of units digit)
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 279
Joined: Wed Sep 24, 2008 8:26 am
Location: Portland, OR
Thanked: 6 times

by pbanavara » Mon Dec 08, 2008 7:07 pm
From 1: Since the Tens has to be a factor of the Units - The number has to have a factor which is not 1 and itself. Hence it can't be prime. Trial and error - but took less than 2 mins

- pradeep
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
Master | Next Rank: 500 Posts
Posts: 248
Joined: Mon Aug 11, 2008 9:51 am
Thanked: 13 times

by earth@work » Mon Dec 08, 2008 8:24 pm
cramya wrote:Keep in mind the following:

1) 0 is a multiple of every number
2) 1 is a factor of every number
3) 0 has infinetely many factors (thats why I added 30,40,50,60,... to the list above since the tens digit in each number is a factor of units digit)
cool! "1 is a factor of every number" just slipped my mind while solving this problem.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 574
Joined: Sun Jun 01, 2008 8:48 am
Location: Bangalore
Thanked: 28 times

by vishubn » Mon Dec 08, 2008 9:31 pm
Cramya: 23 is not composite !! but arent we supposed t oconsider only numbers which are composite ! and wit hthis how can u proce D is Insuff!

I am sure i am askign somethign simple ! but i dont get it !! sorry

VIshu
KILL !! DIE !! or BEAT my FEAR !!! de@D END!!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 2467
Joined: Thu Aug 28, 2008 6:14 pmFollowed by: 11 members
Thanked: 331 times

by cramya » Mon Dec 08, 2008 9:34 pm
Cramya: 23 is not composite !! but arent we supposed t oconsider only numbers which are composite ! and wit hthis how can u proce D is Insuff!

I am sure i am askign somethign simple ! but i dont get it !! sorry
No probs Vishu!

U r correct. . 23 is prime and not composite.

Stmt II says 2 digit number greater than 20 with tens digit of 2

If its 23 then its prime
If its 24 then its composite

INSUFF since 2 different answers (hence D) not possible)


In the problem they have given the definition of a composite number which is a bonus and they are not telling us that we need to consider only composites.

Hope this helps!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Legendary Member
Posts: 574
Joined: Sun Jun 01, 2008 8:48 am
Location: Bangalore
Thanked: 28 times

by vishubn » Mon Dec 08, 2008 9:38 pm
In the problem they have given the definition of a composite number which is a bonus and they are not telling us that we need to consider only composites.
More than the solution , the statement helped :) thanks cramya ! i am sure i am all konked :)

thanks again

Vishu
KILL !! DIE !! or BEAT my FEAR !!! de@D END!!
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1