absolute value

Expert replies

artstudent: Senior | Next Rank: 100 Posts; Posts: 62; Joined: Mon Mar 28, 2011 9:35 pm; Thanked: 4 times

by artstudent » Wed Jul 20, 2011 9:48 pm

For any non-zero a and b that satisfy |ab| = ab and |a| = -a
|b - 4| + |ab - b| =

A. ab - 4
B. 2b - ab - 4
C. ab + 4
D. ab - 2b + 4
E. 4 - ab

Like this post

Source: Beat The GMAT — Problem Solving | Wed Jul 20, 2011 9:48 pm

winniethepooh: Master | Next Rank: 500 Posts; Posts: 370; Joined: Sat Jun 11, 2011 8:50 pmFollowed by: 2 members; Location: Arlington, MA.; Thanked: 27 times

by winniethepooh » Wed Jul 20, 2011 10:21 pm

IMO answer is c
As |ab|= ab and |a|= -a, therefore even |b| should be -b as -a*-b = ab

|b-4|+ |ab-b| = -b +4 + ab - b = 4 + ab - 2b.
Hence, D.

Last edited by winniethepooh on Wed Jul 20, 2011 11:01 pm, edited 1 time in total.

Like this post

GMAT/MBA Expert

Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members; Location: Milpitas, CA; Thanked: 1854 times; GMAT Score:770

by Anurag@Gurome » Wed Jul 20, 2011 10:26 pm

artstudent wrote:For any non-zero a and b that satisfy |ab| = ab and |a| = -a
|b - 4| + |ab - b| =

A. ab - 4
B. 2b - ab - 4
C. ab + 4
D. ab - 2b + 4
E. 4 - ab

Solution
labl = ab means ab > 0.
lal = -a means a < 0.
This implies b < 0.
b-4 < 0
lb-4l = 4 - b.
ab - b > 0
lab-bl = ab - b
lb-4l + lab-bl = 4 + ab - 2b.

The correct answer is D.

Anurag Mairal, Ph.D., MBA
GMAT Expert, Admissions and Career Guidance
Gurome, Inc.
1-800-566-4043 (USA)

Join Our Facebook Groups
GMAT with Gurome
https://www.facebook.com/groups/272466352793633/
Admissions with Gurome
https://www.facebook.com/groups/461459690536574/
Career Advising with Gurome
https://www.facebook.com/groups/360435787349781/

Like this post

winniethepooh: Master | Next Rank: 500 Posts; Posts: 370; Joined: Sat Jun 11, 2011 8:50 pmFollowed by: 2 members; Location: Arlington, MA.; Thanked: 27 times

by winniethepooh » Wed Jul 20, 2011 10:35 pm

Sir, any logic behind |b-4|= 4-b? Though I understand that |b|= -b, so b < 0 and b-4 < 0.

Like this post

GMAT/MBA Expert

Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pmFollowed by: 523 members; Location: Milpitas, CA; Thanked: 1854 times; GMAT Score:770

by Anurag@Gurome » Wed Jul 20, 2011 10:40 pm

winniethepooh wrote:Sir, any logic behind |b-4|= 4-b? Though I understand that |b|= -b, so b < 0 and b-4 < 0.

By definition, |x| = -x if x < 0
As (b - 4) < 0, |b - 4| = -(b - 4) = (4 - b)

Like this post

winniethepooh: Master | Next Rank: 500 Posts; Posts: 370; Joined: Sat Jun 11, 2011 8:50 pmFollowed by: 2 members; Location: Arlington, MA.; Thanked: 27 times

by winniethepooh » Wed Jul 20, 2011 10:49 pm

Thanks for your help. I really appreciate it!
A note in my Points to Remember!

Like this post

amit2k9: Master | Next Rank: 500 Posts; Posts: 461; Joined: Tue May 10, 2011 9:09 amFollowed by: 3 members; Location: pune; Thanked: 36 times

by amit2k9 » Thu Jul 21, 2011 1:36 am

ab > 0 and a < 0 meaning b <0.

hence let a=b= -1 each. thus the equation provides 7 as its value.

now checking for a,b,c,d and e we find b and d providing -7 and 7 respectively.

thus D it is.

For Understanding Sustainability,Green Businesses and Social Entrepreneurship visit -https://aamthoughts.blocked/
(Featured Best Green Site Worldwide-https://bloggers.com/green/popular/page2)

Like this post

artstudent: Senior | Next Rank: 100 Posts; Posts: 62; Joined: Mon Mar 28, 2011 9:35 pm; Thanked: 4 times

by artstudent » Thu Jul 21, 2011 8:21 pm

how did you get -1?

Like this post

Post new topic Post Reply

• Page 1 of 1

GMAT Course Reviews

559 reviews

1168 reviews

431 reviews

359 reviews

147 reviews

5/5

5 Star (560 Reviews)

"Target Test Prep is the closest to the official version of the GMAT exam, about 99% accuracy in terms of the quality and quantity of information. The course has excellently created singular sets of focused lessons and tests for every possible topic that one could come across in the official GMAT exam."

"The TTP course maximizes the efficiency of the time you spend studying. It will take time and effort but I could almost guarantee that if you complete the course exactly as it is laid out you will get an amazing score. They also have a very responsive team willing to help with any questions you might have."

"TTP has two things that I think no other test prep company offers: A teaching approach that reinforces understanding and an attitude that will give you the mental preparedness needed to succeed on the test. TTP gives you a deep understanding of the concept you need to know while teaching you how to think."

Write a Review