NEW HERE? LEARN MORE
closeclose
Last visit was: 29 Apr 2024, 03:42 It is currently 29 Apr 2024, 03:42
Decision Tracker
My Rewards
New posts
New comers' posts

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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

If 4/(5 - a/b) = 1, which of the following must be true?

SORT BY:
Date
Kudos
Tags:
Find Similar Topics 
Show Tags
Hide Tags
User avatar
Silviax
Manager
Manager
Joined: 14 Jun 2012
Posts: 107
Own Kudos [?]: 82 [5]
Given Kudos: 28
Concentration: International Business
GMAT 1: 560 Q36 V31
GMAT 2: 580 Q39 V31
GMAT 3: 630 Q41 V35
GPA: 4
Send PM
Reviews Badge
If 4/(5 - a/b) = 1, which of the following must be true? [#permalink] New post   06 Jun 2016, 09:10
1
Kudos
4
Bookmarks
00:00
A
B
C
D
E

Difficulty:

5% (low)

Question Stats:

95% (00:48) correct 5% (01:11) wrong based on 216 sessions
Hide Show timer Statistics
If \(\frac{4}{5 - \frac{a}{b}} = 1\) which of the following must be true?

(A) a = 0
(B) b = 0
(C) a = 1
(D) b = 1
(E) a = b
ShowHide Answer
Official Answer
E
User avatar
L
BrentGMATPrepNow
GMAT Club Legend
GMAT Club Legend
Joined: 12 Sep 2015
Posts: 6818
Own Kudos [?]: 29988 [1]
Given Kudos: 799
Location: Canada
Send PM
Re: If 4/(5 - a/b) = 1, which of the following must be true? [#permalink] New post   06 Jun 2016, 09:38
1
Kudos
Expert Reply
Top Contributor
Silviax wrote:
Please merge if the topic already exists. I couldn't find it. Thank you.

If \(\frac{4}{5-a/b}=1\) which of the following must be true?

(A) a= 0
(B) b= 0
(C) a=1
(D) b=1
(E) a=b


Chetan2u has done a great job applying what I call the Something Method.

Given: \(\frac{4}{5-a/b}=1\)
So, we have: 4/something = 1
This means that something = 4
In other words, 5 - a/b = 4

Now we have 5 - a/b = 4
If 5 - something = 4, then something = 1
In other words, a/b = 1
If a/b = 1, then we can be certain that a = b

Answer:
Show Spoiler
E


Here's a video on the Something Method:
Something Method
[youtube]https://www.youtube.com/watch?v=mmTisgtNfTI[/youtube]
User avatar
Silviax
Manager
Manager
Joined: 14 Jun 2012
Posts: 107
Own Kudos [?]: 82 [0]
Given Kudos: 28
Concentration: International Business
GMAT 1: 560 Q36 V31
GMAT 2: 580 Q39 V31
GMAT 3: 630 Q41 V35
GPA: 4
Send PM
Reviews Badge
Re: If 4/(5 - a/b) = 1, which of the following must be true? [#permalink] New post   06 Jun 2016, 09:17
I just figured out the answer to my problem.
if x = y then no matter what these numbers of this second fraction are it will be 1. A number divided by itself = 1.
So 5-1 = 4 and that's exactly what I need as the denominator by which to divide the numerator in order to get 1.

:idea:
User avatar
L
chetan2u
RC & DI Moderator
Joined: 02 Aug 2009
Status:Math and DI Expert
Posts: 11184
Own Kudos [?]: 32040 [1]
Given Kudos: 291
Send PM
Reviews Badge
Re: If 4/(5 - a/b) = 1, which of the following must be true? [#permalink] New post   06 Jun 2016, 09:17
1
Bookmarks
Expert Reply
Silviax wrote:
Please merge if the topic already exists. I couldn't find it. Thank you.

If \(\frac{4}{5-a/b}=1\) which of the following must be true?

(A) a= 0
(B) b= 0
(C) a=1
(D) b=1
(E) a=b


\(\frac{4}{5-a/b}=1\) .....
fraction can be 1 when numerator and denominator are equal, so \(4 = 5- \frac{a}{b}\)..........\(\frac{a}{b} = 5-4 = 1........a=b\)
E
User avatar
L
Abhishek009
Board of Directors
Joined: 11 Jun 2011
Status:QA & VA Forum Moderator
Posts: 6072
Own Kudos [?]: 4691 [0]
Given Kudos: 463
Location: India
GPA: 3.5
WE:Business Development (Commercial Banking)
Send PM
GMAT ToolKit User
Re: If 4/(5 - a/b) = 1, which of the following must be true? [#permalink] New post   27 Sep 2018, 07:25
Silviax wrote:
Please merge if the topic already exists. I couldn't find it. Thank you.

If \(\frac{4}{5-a/b}=1\) which of the following must be true?

(A) a= 0
(B) b= 0
(C) a=1
(D) b=1
(E) a=b

\(\frac{4}{5-a/b}=1\)

Or, \(4 = 5 - \frac{a}{b}\)

So, \(\frac{a}{b} = 1\)

Thus, \(a = b\) , Answer must be (E)
User avatar
D
BrushMyQuant
Tutor
Joined: 05 Apr 2011
Status:Tutor - BrushMyQuant
Posts: 1778
Own Kudos [?]: 2096 [1]
Given Kudos: 100
Location: India
Concentration: Finance, Marketing
Schools: XLRI (A)
GMAT 1: 700 Q51 V31
GPA: 3
WE:Information Technology (Computer Software)
Send PM
Re: If 4/(5 - a/b) = 1, which of the following must be true? [#permalink] New post   10 Dec 2023, 08:44
Expert Reply
Top Contributor
\(\frac{4}{5 - \frac{a}{b}} = 1\)

=> 4 = 5 - \(\frac{a}{b}\)
=> \(\frac{a}{b}\) = 5 - 4 = 1

Since b is in the denominator
=> b ≠ 0

\(\frac{a}{b}\) = 1
=> a = b will always be true

So, Answer will be E
Hope it helps!
User avatar
B
uCS2020
Intern
Intern
Joined: 02 Aug 2020
Posts: 38
Own Kudos [?]: 20 [0]
Given Kudos: 249
Re: If 4/(5 - a/b) = 1, which of the following must be true? [#permalink] New post   10 Dec 2023, 09:07
To solve this question,
4/5-a/b I first found out what 5-a/b is
It’s is = to 5b-a/b
Let’s substitute it
4/5b-a/b = 4b/5b-a = 1
Now,what we need to know is that if a fraction is = 1 then both the numerator and denominator are the same
Let’s make an equation

4b = 5b-a
Add a from both sides
4b+a = 5b
Subtract 4b from each side
a=b


Answer = E

Posted from my mobile device
GMAT Club Bot
gmatclubot
Re: If 4/(5 - a/b) = 1, which of the following must be true? [#permalink]
10 Dec 2023, 09:07
Moderators:
Bunuel
Math Expert
92990 posts
yashikaaggarwal
Senior Moderator - Masters Forum
3137 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions