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 →

"must be true" question??

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Junior | Next Rank: 30 Posts
Posts: 15
Joined: Fri Jun 18, 2010 6:56 am
by ohjoon2 » Fri Jun 18, 2010 7:01 am
i'm stuck on this simple algebra inequality question..
i thought the answer was E, but my prep book says the answer is C..
but C indicates that z can be ANY number greater than -8 meaning it could be 10, or 100, or 1million.
this doesn't make any sense to me because the question stem specifically states z is less than 8.
BUT i can see WHY c might be correct because in some ways, yes z must be greater than -8
it seems that i'm thinking too inclusively..
are all GMAT Math "must be true" questions the same way?
i feel it's ambigious

If it is true that z < 8 and 2z > -4, which of the following must be true?
a) -8 < z < 4
b) z > 2
c) z > -8
d) z < 4
e) none of the above
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 265
Joined: Mon Dec 28, 2009 9:45 pmFollowed by: 2 members
Thanked: 26 times
GMAT Score:760

by mj78ind » Fri Jun 18, 2010 7:10 am
ohjoon2 wrote:i'm stuck on this simple algebra inequality question..
i thought the answer was E, but my prep book says the answer is C..
but C indicates that z can be ANY number greater than -8 meaning it could be 10, or 100, or 1million.
this doesn't make any sense to me because the question stem specifically states z is less than 8.
BUT i can see WHY c might be correct because in some ways, yes z must be greater than -8
it seems that i'm thinking too inclusively..
are all GMAT Math "must be true" questions the same way?
i feel it's ambigious

If it is true that z < 8 and 2z > -4, which of the following must be true?
a) -8 < z < 4
b) z > 2
c) z > -8
d) z < 4
e) none of the above
Dude I would change the prep book since you are better than it............
8<z<-2, none of the choices except E satisfies it and this is a pretty simple problem to goof up in by a prep book.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 147
Joined: Tue Aug 25, 2009 7:57 pmFollowed by: 17 members
Location: New York City
Thanked: 76 times
GMAT Score:770

by Rich@VeritasPrep » Fri Jun 18, 2010 7:10 am
Hey there,

It's not ambiguous. As you said, because -2 < z < 8, it MUST BE TRUE that -8 < z.

I think you're confusing the following two ideas, which are different:

a. -8 < z must be true
b. -8 < z gives all possible solutions

When we say it must be true that z > -8, we're not saying that z an be ANY VALUE greater than -8. We're just saying that whatever value z is, it will DEFINITELY be greater than -8.
Rich Zwelling
GMAT Instructor, Veritas Prep
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 265
Joined: Mon Dec 28, 2009 9:45 pmFollowed by: 2 members
Thanked: 26 times
GMAT Score:760

by mj78ind » Fri Jun 18, 2010 7:15 am
raz1024 wrote:Hey there,

It's not ambiguous. As you said, because -2 < z < 8, it MUST BE TRUE that -8 < z.

I think you're confusing the following two ideas, which are different:

a. -8 < z must be true
b. -8 < z gives all possible solutions

When we say it must be true that z > -8, we're not saying that z an be ANY VALUE greater than -8. We're just saying that whatever value z is, it will DEFINITELY be greater than -8.
Yup you got me there Raz!
I owe an apology to the book and ohjoon!!

Hey Raz I got you on one of the others, so we are even :)

Thanks much though seriously, your posts are good.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
User avatar
GMAT Instructor
Posts: 147
Joined: Tue Aug 25, 2009 7:57 pmFollowed by: 17 members
Location: New York City
Thanked: 76 times
GMAT Score:770

by Rich@VeritasPrep » Fri Jun 18, 2010 7:20 am
You're welcome! Pleasure to help.

And yes, it's true...even teachers make mistakes.

Yes, I know...hard to believe :-P
Rich Zwelling
GMAT Instructor, Veritas Prep
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1