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

Redeem

Problem solving

Problem Solving — algebra and arithmetic (GMAT Focus Edition)
This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 39
Joined: Thu Apr 23, 2015 10:30 pm
Thanked: 1 times

Problem solving

by Newaz111 » Mon May 04, 2015 6:03 am
In the xy-plane, the points (c, d), (c, -d), and (-c, -d) are three vertices of a certain square. If c < 0 and d > 0, which of the following points is in the same quadrant as the fourth vertex of the square?

A. (-5, -3)
B. (-5, 3)
C. (5, -3)
D. (3, -5)
E. (3, 5)
Top
Source: — Quantitative Reasoning |

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] » Mon May 04, 2015 11:34 am
Hi Newaz111,

This question really tests your attention-to-detail and organizational skills. If you "slip" a negative sign incorrectly, then you'll get the question wrong, thus a certain amount of note-taking is necessary.

We're told that C < 0 and D > 0, so let's start by TESTing VALUES....

IF.....
C = -2,
D = 2

The 3 co-ordinates that we're given will become...

(C,D) = (-2, 2) --> Quadrant 2
(C,-D) = (-2, -2) --> Quadrant 3
(-C,-D) = (2, -2) --> Quadrant 4

The last co-ordinate of the square will be in Quadrant 1, which means we need a POSITIVE X-co-ordinate and a POSITIVE Y-co-ordinate....

Final Answer: E

GMAT assassins aren't born, they're made,
Rich
Contact Rich at [email protected]
Image
Top
User avatar
GMAT Instructor
Posts: 1035
Joined: Fri Dec 17, 2010 11:13 am
Location: Los Angeles, CA
Thanked: 474 times
Followed by:365 members

by VivianKerr » Sun May 24, 2015 9:55 pm
It might help you to visualize by drawing the vertices of the square.

Remember this rule on the GMAT: you are given limitations on variables for a reason.

Why would they tell us that c < 0 and d > 0? It must matter somehow.

If c is always negative, then (c, d) will become (-c, d), since a positive number multiplied by a negative number is always negative. The "d" will not be affected, since a positive multiplied by a positive is always positive.

By the same line of thinking:

(c, -d) = (-c, -d)
(-c, -d) = (c, -d)

Let's plot (-c, d), (-c, -d), and (c, -d) on the coordinate grid, and it will be easy to see the missing quadrant.

Image

The first quadrant, in which "c" and "d" are positive, is missing. Look for an answer choice with a positive value for both x and y. It must be [spoiler](E)[/spoiler].
Vivian Kerr
GMAT Rockstar, Tutor
https://www.GMATrockstar.com
https://www.yelp.com/biz/gmat-rockstar-los-angeles

Former Kaplan and Grockit instructor, freelance GMAT content creator, now offering affordable, effective, Skype-tutoring for the GMAT at $150/hr. Contact: [email protected]

Thank you for all the "thanks" and "follows"! :-)
Top
Post new topic Post Reply
• Page 1 of 1