It is currently 18 Jan 2018, 12:06

Close

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
Your Progress

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.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If a – b = 7 and 2ab = 18 then a^2 + b^2 =

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

Hide Tags

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 43323

Kudos [?]: 139428 [0], given: 12790

If a – b = 7 and 2ab = 18 then a^2 + b^2 = [#permalink]

Show Tags

New post 12 Sep 2017, 04:22
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

75% (01:40) correct 25% (01:21) wrong based on 67 sessions

HideShow timer Statistics

Kudos [?]: 139428 [0], given: 12790

BSchool Forum Moderator
User avatar
D
Joined: 26 Feb 2016
Posts: 1805

Kudos [?]: 825 [0], given: 22

Location: India
Concentration: General Management, Leadership
WE: Sales (Retail)
Premium Member CAT Tests
If a – b = 7 and 2ab = 18 then a^2 + b^2 = [#permalink]

Show Tags

New post 12 Sep 2017, 04:28
Bunuel wrote:
If a – b = 7 and 2ab = 18 then a^2 + b^2 =

A. 67
B. 49
C. 40
D. 31
E. 14


Formula used : \((a-b)^2 = a^2 + b^2 - 2ab\)

Therefore, \(a^2 + b^2 = (a-b)^2 +2ab\)
Substituting values,
\(a^2 + b^2 = (7)^2 +18 = 49 + 18 = 67\)(Option A)
_________________

Stay hungry, Stay foolish

2017-2018 MBA Deadlines

Class of 2020: Rotman Thread | Schulich Thread
Class of 2019: Sauder Thread

Kudos [?]: 825 [0], given: 22

Manager
Manager
User avatar
B
Joined: 19 Jul 2017
Posts: 85

Kudos [?]: 13 [0], given: 85

Location: India
Concentration: General Management, Strategy
GPA: 3.5
Re: If a – b = 7 and 2ab = 18 then a^2 + b^2 = [#permalink]

Show Tags

New post 12 Sep 2017, 23:21
Bunuel wrote:
If a – b = 7 and 2ab = 18 then a^2 + b^2 =

A. 67
B. 49
C. 40
D. 31
E. 14

a^2+b^2= (a-b)^2+2ab= 7^2+18=49+18=67
Ans:A

Kudos [?]: 13 [0], given: 85

Expert Post
1 KUDOS received
Target Test Prep Representative
User avatar
S
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 1820

Kudos [?]: 1048 [1], given: 5

Re: If a – b = 7 and 2ab = 18 then a^2 + b^2 = [#permalink]

Show Tags

New post 15 Sep 2017, 09:07
1
This post received
KUDOS
Expert's post
Bunuel wrote:
If a – b = 7 and 2ab = 18 then a^2 + b^2 =

A. 67
B. 49
C. 40
D. 31
E. 14


We can square the first equation and we have:

(a – b)^2 = 7^2

a^2 - 2ab + b^2 = 49

Substituting 18 for 2ab, we have:

a^2 - 18 + b^2 = 49

a^2 + b^2 = 67

Answer: A
_________________

Jeffery Miller
Head of GMAT Instruction

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Kudos [?]: 1048 [1], given: 5

Re: If a – b = 7 and 2ab = 18 then a^2 + b^2 =   [#permalink] 15 Sep 2017, 09:07
Display posts from previous: Sort by

If a – b = 7 and 2ab = 18 then a^2 + b^2 =

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


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

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

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.