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

Redeem

Manhattan Question Set # 9

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
User avatar
Legendary Member
Posts: 698
Joined: Tue Jul 21, 2015 12:12 am
Location: Noida, India
Thanked: 32 times
Followed by:26 members
GMAT Score:740

Manhattan Question Set # 9

by richachampion » Sun Oct 09, 2016 6:01 pm
If (a - b)c < 0, which of the following cannot be true?

A. a < b
B. c < 0
C. |c| < 1
D. ac > bc
E. a² - b² > 0

OA: D
R I C H A,
My GMAT Journey: 470 → 720 → 740
Target Score: 760+
[email protected]
1. Press thanks if you like my solution.
2. Contact me if you are not improving. (No Free Lunch!)
Top
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
Elite Legendary Member
Posts: 10392
Joined: Sun Jun 23, 2013 6:38 pm
Location: Palo Alto, CA
Thanked: 2867 times
Followed by:511 members
GMAT Score:800

by [email protected] » Sun Oct 09, 2016 8:27 pm
Hi richachamption,

While this question looks 'thin', it might take longer to solve than you first think - since the question asks which of the 5 answers CANNOT be true, you might want to prove that 4 of the answers COULD be true (meaning that whichever answer is left would be the correct one) - and that will take a bit of work.

We're told that (A - B)(C) < 0. This means that...
(A - B) = negative and C = positive

OR

(A - B) = positive and C = negative

Answer A: A < B. IF (A - B) is negative, then we could have A=1 and B=2. Eliminate Answer A

Answer B: C < 0. C could be negative (as discussed above). Eliminate Answer B

Answer C: |C| < 1. C could be a positive fraction or a negative fraction (see above). Eliminate Answer C

Between the remaining two answers, Answer E focuses on just 2 of the variables, so I'll deal with that answer first...

Answer E: A^2 - B^2 > 0. IF (A - B) is positive, then we could have A=2 and B=1. Eliminate Answer E

Final Answer: D

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
Image
Top
User avatar
GMAT Instructor
Posts: 15539
Joined: Tue May 25, 2010 12:04 pm
Location: New York, NY
Thanked: 13060 times
Followed by:1906 members
GMAT Score:790

by GMATGuruNY » Mon Oct 10, 2016 5:57 am
richachampion wrote:If (a - b)c < 0, which of the following cannot be true?

A. a < b
B. c < 0
C. |c| < 1
D. ac > bc
E. a² - b² > 0
(a-b)c < 0
ab - bc < 0
ab < bc.

Thus, D cannot be true.

The correct answer is D.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.

As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.

For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Top
GMAT Instructor
Posts: 2630
Joined: Wed Sep 12, 2012 3:32 pm
Location: East Bay all the way
Thanked: 625 times
Followed by:119 members
GMAT Score:780

by Matt@VeritasPrep » Fri Oct 14, 2016 2:26 am
Factored out, the prompt gives us

ac - bc < 0

But D says that

ac > bc, or

ac - bc > 0

which is the opposite!
Top
Post new topic Post Reply
• Page 1 of 1