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

It is currently 20 Aug 2019, 16:20

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

If (a – b)(a + b) = 7 x 13, then which one of the following pairs coul

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

Hide Tags

Find Similar Topics 
Manager
Manager
avatar
G
Joined: 26 Dec 2018
Posts: 142
Location: India
If (a – b)(a + b) = 7 x 13, then which one of the following pairs coul  [#permalink]

Show Tags

New post 05 Jan 2019, 10:32
1
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

57% (01:12) correct 43% (01:33) wrong based on 35 sessions

HideShow timer Statistics

If (a – b)(a + b) = 7 x 13, then which one of the following pairs could be the values of a and b, respectively?

(A) 7, 13
(B) 5, 15
(C) 3, 10
(D) –10, 3
(E) –3, –10

Source: Nova GMAT
Difficulty Level: 650

_________________
GOOD LUCK!
Manager
Manager
avatar
B
Joined: 01 May 2017
Posts: 82
Location: India
Re: If (a – b)(a + b) = 7 x 13, then which one of the following pairs coul  [#permalink]

Show Tags

New post 05 Jan 2019, 19:09
2
If \((a – b)(a + b) = 7*13\), then which one of the following pairs could be the values of a and b, respectively?

In the above equation both a-b and a+b may result in positive or the negative values(cancel out the sign)
Since 7,13 are prime we can consider a-b = 7, a+b = 13 OR a-b = -7 and a+b = -13 OR a-b = -13 , a+b = -7 ....So many possibilities

Better
We can go with option verification,
Only option D satisfies,
Option D implies,
\(a+b = -10+3 = -7\)
\(a-b = -10-3 = -13\)
satisfying the condition \((a-b)(a+b) = 7*13\)
Option D is correct
VP
VP
User avatar
D
Joined: 31 Oct 2013
Posts: 1429
Concentration: Accounting, Finance
GPA: 3.68
WE: Analyst (Accounting)
CAT Tests
Re: If (a – b)(a + b) = 7 x 13, then which one of the following pairs coul  [#permalink]

Show Tags

New post 06 Jan 2019, 04:50
UB001 wrote:
If (a – b)(a + b) = 7 x 13, then which one of the following pairs could be the values of a and b, respectively?

(A) 7, 13
(B) 5, 15
(C) 3, 10
(D) –10, 3
(E) –3, –10


\((a-b)(a+b) = a^2 -b^2\)

\(a^2 -b^2 = 7*13\)

\(a^2 - b^2 =91.\)

\((-10)^2 -(3)^2 = 91\)

Thus correct answer is D.

GMAT experts always say that test takers see the answer choices first. here is the key .
GMAT Club Bot
Re: If (a – b)(a + b) = 7 x 13, then which one of the following pairs coul   [#permalink] 06 Jan 2019, 04:50
Display posts from previous: Sort by

If (a – b)(a + b) = 7 x 13, then which one of the following pairs coul

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





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