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If 4/ (5-a/b) = 1

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If 4/ (5-a/b) = 1  [#permalink]

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New post 06 Jun 2016, 09:10
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A
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E

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Question Stats:

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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
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Joined: 14 Jun 2012
Posts: 112
Concentration: International Business
GMAT 1: 560 Q36 V31
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Re: If 4/ (5-a/b) = 1  [#permalink]

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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:
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Re: If 4/ (5-a/b) = 1  [#permalink]

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New post 06 Jun 2016, 09:17
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
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3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html


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Re: If 4/ (5-a/b) = 1  [#permalink]

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New post 06 Jun 2016, 09:38
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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:

Here's a video on the Something Method:
Something Method

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Re: If 4/ (5-a/b) = 1  [#permalink]

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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)
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Re: If 4/ (5-a/b) = 1 &nbs [#permalink] 27 Sep 2018, 07:25
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