GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 15 Oct 2019, 02:30 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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.  For real numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5)

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics
Author Message
TAGS:

Hide Tags

Math Expert V
Joined: 02 Sep 2009
Posts: 58353
For real numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5)  [#permalink]

Show Tags 00:00

Difficulty:   5% (low)

Question Stats: 90% (00:57) correct 10% (00:50) wrong based on 40 sessions

HideShow timer Statistics

For numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5) ?

(A) -72
(B) -27
(C) -24
(D) 24
(E) 72

_________________
Intern  B
Joined: 05 Mar 2019
Posts: 16
Re: For real numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5)  [#permalink]

Show Tags

Following the steps through we get first 3?(-9) and as a result -72.

Director  G
Joined: 22 Nov 2018
Posts: 557
Location: India
GMAT 1: 640 Q45 V35 GMAT 2: 660 Q48 V33 Re: For real numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5)  [#permalink]

Show Tags

4?5 is -9 and 3?-9 (9-81, x^2-y^2) gives -72. Option A

Posted from my mobile device
_________________
Give +1 kudos if this answer helps..!!
GMAT Club Legend  D
Joined: 18 Aug 2017
Posts: 4994
Location: India
Concentration: Sustainability, Marketing
GPA: 4
WE: Marketing (Energy and Utilities)
Re: For real numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5)  [#permalink]

Show Tags

Bunuel wrote:
For numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5) ?

(A) -72
(B) -27
(C) -24
(D) 24
(E) 72

solve for the expression as per expression we get
3?(-9)
then
-72
IMOA
Target Test Prep Representative D
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 8043
Location: United States (CA)
Re: For real numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5)  [#permalink]

Show Tags

Bunuel wrote:
For numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5) ?

(A) -72
(B) -27
(C) -24
(D) 24
(E) 72

We see that x?y is x^2 - y^2,

Thus, 4?5 = 4^2 - 5^2 = 16 - 25 = -9, and therefore,

3?(-9) = 3^2 - (-9)^2 = 9 - 81 = -72

_________________

Scott Woodbury-Stewart

Founder and CEO

Scott@TargetTestPrep.com

See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews

If you find one of my posts helpful, please take a moment to click on the "Kudos" button. Re: For real numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5)   [#permalink] 27 Mar 2019, 19:11
Display posts from previous: Sort by

For real numbers x and y, define x?y = (x + y)(x - y). What is 3?(4?5)

 new topic post reply Question banks Downloads My Bookmarks Reviews Important topics

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne  