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

Redeem

Which of the following points could lie in the same quadrant

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Source: — Problem Solving |

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 3008
Joined: Mon Aug 22, 2016 6:19 am
Location: Grand Central / New York
Thanked: 470 times
Followed by:34 members

by Jay@ManhattanReview » Mon Sep 10, 2018 9:29 pm
BTGmoderatorDC wrote:Which of the following points could lie in the same quadrant of the xy-coordinate plane as the point (a, b), where ab ≠ 0 ?

A. (-b, -a)
B. (-a, -b)
C. (b, -a)
D. (a, -b)
E. (-b, a)

OA A

Source: Manhattan Prep
Hello BTGmoderatorDC,

Pl. first search a question and then post. This question is already asked and replied last month. Pl. find it here.

https://www.beatthegmat.com/which-of-th ... tml#818626

Hope this helps!

-Jay
_________________
Manhattan Review GRE Prep

Locations: GMAT Classes Chicago | GRE Prep Course San Diego | GRE Prep Atlanta | TOEFL Prep Classes Houston | and many more...

Schedule your free consultation with an experienced GMAT Prep Advisor! Click here.
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 16207
Joined: Mon Dec 08, 2008 6:26 pm
Location: Vancouver, BC
Thanked: 5254 times
Followed by:1268 members
GMAT Score:770

by Brent@GMATPrepNow » Tue Sep 11, 2018 6:02 am
BTGmoderatorDC wrote:Which of the following points could lie in the same quadrant of the xy-coordinate plane as the point (a, b), where ab ≠ 0 ?

A. (-b, -a)
B. (-a, -b)
C. (b, -a)
D. (a, -b)
E. (-b, a)
Let's test some coordinates...

How about: a = 1 and b = -2.
This means the point (a, b) = (1, -2), which is in QUADRANT IV

Now plug a = 1 and b = -2 into each answer choice...

A) (-b, -a) = [( -(-2), -1] = (2, -1), which is also in QUADRANT IV
PERFECT!

Answer: A

Cheers,
Brent
Brent Hanneson - Creator of GMATPrepNow.com
Image
Top
User avatar
GMAT Instructor
Posts: 1449
Joined: Sat Oct 09, 2010 2:16 pm
Thanked: 59 times
Followed by:33 members

by fskilnik@GMATH » Tue Sep 11, 2018 7:59 am
BTGmoderatorDC wrote:Which of the following points could lie in the same quadrant of the xy-coordinate plane as the point (a, b), where ab ≠ 0 ?

A. (-b, -a)
B. (-a, -b)
C. (b, -a)
D. (a, -b)
E. (-b, a)

Source: Manhattan Prep
Just a quick observation that is (I hope) interesting in its own right:

If x*y and w*z are both different from zero, points (x,y) and (w,z) will be in the same quadrant if, and only if,
x*w> 0 ("x-coordinates" have the same sign) and y*z>0 ("y-coordinates" have the same sign).

Conclusion:

(B) is refuted, because a and -a (x-coordinates in question stem and in this alternative choice) do not have the same signs (a is not zero)
(C) is refuted, because if a and b (x-coordinates...) have the same signs , then b and -a (y-coordinates...) don´t have
(D) is refuted, because b and -b (y-coordinates...) do not have the same signs (b is not zero)
(E) is refuted, because if a and -b (x-coordinates...) have the same signs , then b and a (y-coordinates...) don´t have

Regards,
fskilnik.
Fabio Skilnik :: GMATH method creator ( Math for the GMAT)
English-speakers :: https://www.gmath.net
Portuguese-speakers :: https://www.gmath.com.br
Top

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 8086
Joined: Sat Apr 25, 2015 10:56 am
Location: Los Angeles, CA
Thanked: 43 times
Followed by:29 members

by Scott@TargetTestPrep » Wed Sep 12, 2018 5:44 pm
BTGmoderatorDC wrote:Which of the following points could lie in the same quadrant of the xy-coordinate plane as the point (a, b), where ab ≠ 0 ?

A. (-b, -a)
B. (-a, -b)
C. (b, -a)
D. (a, -b)
E. (-b, a)
Let's suppose that (a, b) lies in Quadrant IV. That is, a is positive and b is negative.

Thus, -b is positive and -a is negative, so (-b, -a) also lies in Quadrant IV.

Alternate Solution:

If we assume that both a and b are positive, and thus (a, b) is in Quadrant I, we see that none of the answer choices will lie in Quadrant I.

Now let's assume that a is positive (a = 1) and b is negative (b = -2); then (1, -2) lies in Quadrant IV. Looking at the answer choices, we see that choice A gives us (-b, -a) =(2, -1), which is also in Quadrant IV.

Answer: A

Scott Woodbury-Stewart
Founder and CEO
[email protected]

Image

See why Target Test Prep is rated 5 out of 5 stars on BEAT the GMAT. Read our reviews

ImageImage
Top
Post new topic Post Reply
• Page 1 of 1