It is currently 19 Dec 2018, 04:11

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# If 0.5(y − x) = −1 and x2 − y2 = 24, what is the sum of x

Author Message
TAGS:
GMAT Club Legend
Joined: 07 Jun 2014
Posts: 4756
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 93

Kudos [?]: 1668 [0], given: 396

If 0.5(y − x) = −1 and x2 − y2 = 24, what is the sum of x [#permalink]  17 Mar 2018, 07:28
Expert's post
00:00

Question Stats:

100% (00:45) correct 0% (00:00) wrong based on 5 sessions
If 0.5(y − x) = −1 and $$x^2 - y^2 = 24$$, what is the sum of x and y ?
A. −48
B. −12
C. 6
D. 12
E. 48

Drill 2
Question: 6
Page: 497-498
[Reveal] Spoiler: OA

_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test

GMAT Club Legend
Joined: 07 Jun 2014
Posts: 4756
GRE 1: Q167 V156
WE: Business Development (Energy and Utilities)
Followers: 93

Kudos [?]: 1668 [0], given: 396

Re: If 0.5(y − x) = −1 and x2 − y2 = 24, what is the sum of x [#permalink]  18 Mar 2018, 07:02
Expert's post
Explanation

Because $$x^2 - y^2 =(x + y)(x - y) = 24$$, if the value of (x − y) is found, (x + y) can be figured out.

Manipulate the equation 0.5(y − x) = –1 to get (y − x) = –2.

Multiplying both sides by –1, you get x – y = 2.

Substitute this value into the equation (x + y)(x – y) = 24 and then divide both sides of the equation by 2 to get (x + y) = 12. The answer is choice (D).
_________________

Sandy
If you found this post useful, please let me know by pressing the Kudos Button

Try our free Online GRE Test

Re: If 0.5(y − x) = −1 and x2 − y2 = 24, what is the sum of x   [#permalink] 18 Mar 2018, 07:02
Display posts from previous: Sort by