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

It is currently 20 Aug 2019, 17:50

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

In the system of equations above, what is the value of b?

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

Hide Tags

Find Similar Topics 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 57155
In the system of equations above, what is the value of b?  [#permalink]

Show Tags

New post 07 Aug 2019, 00:46
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

94% (01:25) correct 6% (01:58) wrong based on 32 sessions

HideShow timer Statistics

Senior Manager
Senior Manager
User avatar
G
Joined: 16 Jan 2019
Posts: 409
Location: India
Concentration: General Management
WE: Sales (Other)
Re: In the system of equations above, what is the value of b?  [#permalink]

Show Tags

New post 07 Aug 2019, 01:12
Adding the two equations we get c=50 and so,

a+b=35
-a-b=-35 which is again a+b=35

So the two are essentially the same equation.

We have one equation and two unknowns so there is not enough information to decide

Answer is (E)

Posted from my mobile device
Intern
Intern
avatar
Joined: 15 Dec 2011
Posts: 1
Re: In the system of equations above, what is the value of b?  [#permalink]

Show Tags

New post 07 Aug 2019, 08:56
To find values of three distinct variables, we need three distinct equations, so the answer is (E).
Target Test Prep Representative
User avatar
D
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 7399
Location: United States (CA)
Re: In the system of equations above, what is the value of b?  [#permalink]

Show Tags

New post 12 Aug 2019, 11:51
Bunuel wrote:
\(a+b+\frac{c}{2}=60\)

\(-a-b+\frac{c}{2}=-10\)

In the system of equations above, what is the value of b?


(A) 8
(B) 20
(C) 35
(D) 50
(E) Not enough information to decide.


Adding the two equations, we have:

c = 50

Substituting, the two equations become:

a + b + 25 = 60

a + b = 35

and

-a - b + 25 = -10

-a - b = -35

a + b = 35

We see that the two equations reduce to a single equation of a + b = 35. Since there are infinitely many values of b which will satisfy this equation, we don’t have enough information to decide on a single value of b which will satisfy this equation.

Alternative solution:

If we subtract the two equations (e.g., subtract the second equation from the first), we have:

2a + 2b = 70

a + b = 35

Since there are infinitely many values of b which will satisfy this equation, we don’t have enough information to decide on a single value of b which will satisfy this equation.


Answer: E
_________________

Scott Woodbury-Stewart

Founder and CEO

Scott@TargetTestPrep.com
TTP - Target Test Prep Logo
122 Reviews

5-star rated online GMAT quant
self study course

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.

GMAT Club Bot
Re: In the system of equations above, what is the value of b?   [#permalink] 12 Aug 2019, 11:51
Display posts from previous: Sort by

In the system of equations above, what is the value of b?

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





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