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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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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, 06:10
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35% (medium)

Question Stats:

71% (01:37) correct 29% (02:11) wrong based on 92 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, 06:21
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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, 17:34
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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, 10:29
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] 27 Feb 2019, 10:29
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