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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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06 Jun 2016, 09:10
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Difficulty:

5% (low)

Question Stats:

91% (01:01) correct 9% (00:48) wrong based on 55 sessions

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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
Manager
Joined: 14 Jun 2012
Posts: 111
GMAT 1: 560 Q36 V31
GMAT 2: 580 Q39 V31
GMAT 3: 630 Q41 V35
GPA: 4
Re: If 4/ (5-a/b) = 1  [#permalink]

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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.

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Re: If 4/ (5-a/b) = 1  [#permalink]

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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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Re: If 4/ (5-a/b) = 1  [#permalink]

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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

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

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