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# If b ≠ 1 and if ab/(a - b) = 1, what is the value of a in terms of b?

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Joined: 02 Sep 2009
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If b ≠ 1 and if ab/(a - b) = 1, what is the value of a in terms of b?  [#permalink]

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13 Dec 2015, 05:10
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35% (medium)

Question Stats:

73% (01:38) correct 27% (02:02) wrong based on 119 sessions

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If b ≠ 1 and if ab/(a - b) = 1, what is the value of a in terms of b?

A. b/(1 - b)
B. (b - 1)/b
C. b/(b + 1)
D. (b + 1)/b
E. (1 - b)/b

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Re: If b ≠ 1 and if ab/(a - b) = 1, what is the value of a in terms of b?  [#permalink]

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13 Dec 2015, 05:21
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Bunuel wrote:
If b ≠ 1 and if ab/(a - b) = 1, what is the value of a in terms of b?

A. b/(1 - b)
B. (b - 1)/b
C. b/(b + 1)
D. (b + 1)/b
E. (1 - b)/b

$$\frac{ab}{(a - b)}$$= 1

ab = a - b

Or, b = a - ab

or, b = a( 1 - b)

Or, $$\frac{b}{(1-b)}$$ = a

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Re: If b ≠ 1 and if ab/(a - b) = 1, what is the value of a in terms of b?  [#permalink]

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13 Dec 2015, 16:34
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Hi All,

This question comes with a particular 'quirk' (one that you probably won't see on Test Day). The GMAT won't test you on the concept of undefined numbers (re: numbers divided by 0), so any time that this concept is a possibility, the question writers have to add a restriction that removes the option that a 0 could occur in the denominator.

Here, we're told that B CANNOT = 1, which is a bit strange because that restriction doesn't seem to impact the original equation much. In fact, it impacts JUST ONE of the answer choices - so you have to ask WHY that restriction is even there. It's actually because that one answer is the correct one.

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Re: If b ≠ 1 and if ab/(a - b) = 1, what is the value of a in terms of b?  [#permalink]

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27 Feb 2019, 09:29
Bunuel wrote:
If b ≠ 1 and if ab/(a - b) = 1, what is the value of a in terms of b?

A. b/(1 - b)
B. (b - 1)/b
C. b/(b + 1)
D. (b + 1)/b
E. (1 - b)/b

Simplifying, we have:

ab = a - b

b = a - ab

b = a(1 - b)

b/(1 - b) = a

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Re: If b ≠ 1 and if ab/(a - b) = 1, what is the value of a in terms of b?  [#permalink]

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15 Jan 2020, 18:42
Well, I couldn't solve. So I thought to use options.

Option A : a=b/(1 - b)

If you solve you get the original equation back. Hence A is the right answer.

Also, the trick by Empower is neat.! (but as Rich said you probably won't see it on the test day)
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Re: If b ≠ 1 and if ab/(a - b) = 1, what is the value of a in terms of b?  [#permalink]

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18 Jan 2020, 04:08
Bunuel wrote:
If b ≠ 1 and if ab/(a - b) = 1, what is the value of a in terms of b?

A. b/(1 - b)
B. (b - 1)/b
C. b/(b + 1)
D. (b + 1)/b
E. (1 - b)/b

Simplifying, we have:

ab = a - b

ab - a = -b

a(b - 1) = -b

a = -b / (b - 1)

a = b / (1 - b)

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# Scott Woodbury-Stewart

Founder and CEO

Scott@TargetTestPrep.com
181 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.

Re: If b ≠ 1 and if ab/(a - b) = 1, what is the value of a in terms of b?   [#permalink] 18 Jan 2020, 04:08
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