Is a > b ? : GMAT Data Sufficiency (DS)
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# Is a > b ?

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Is a > b ? [#permalink]

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25 Aug 2010, 01:11
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Is a > b ?

(1) a/b = 7/10

(2) a = 70/100*b
[Reveal] Spoiler: OA

Last edited by Bunuel on 03 Sep 2015, 01:11, edited 1 time in total.
Renamed the topic and edited the question.
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Re: Is a > b ? [#permalink]

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25 Aug 2010, 02:41
This type of problem is probably solved fastest by picking numbers. The key is to think about positive and negative numbers.

Statement 1:

Cross-multiply to obtain 10*a = 7*b

This will hold true e.g. if a = 7 and b = 10 => a < b, but also if a= -7 and b = -10 => a > b. Hence, statement A is not sufficient.

Statement 2:

I assume the statement reads a = (70 / 100)*b, otherwise it would contradict the first statement. Again cross-multiple and simplify the fraction to obtain 10*a = 7*b.

The second statement doesn't provide you with any additional information. Thus, E is the solution to this problem.
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Re: Is a > b ? [#permalink]

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25 Aug 2010, 02:42
both statements essentially say the same thing.. ratio: a:b=7:10 => 10a=7b;

now just plug in some values to see if you can get any definitive answers:

assume a=7, b=10 or a=14, b=20 and so on.... (a< b)

but there are negative answers as well.... a=-7, b=-10 => a > b

I would go with E.....
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Re: Is a > b ? [#permalink]

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03 Sep 2015, 01:08
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Re: Is a > b ? [#permalink]

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03 Sep 2015, 01:15
Maude wrote:
Is a > b ?

(1) a/b = 7/10

(2) a = 70/100*b

Notice that both statements give us the same info:

(1) a/b = 7/10
(2) a = 70/100*b --> a/b = 70/100 = 7/10.

Thus the answer is either D or E. It's not D because from a/b = 7/10 it could be that (a = 7) < (b = 10) as well as (a = -7) > (b = -10).

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Is a > b ? [#permalink]

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04 Sep 2015, 03:45
Forget conventional ways of solving math questions. In DS, Variable approach is

the easiest and quickest way to find the answer without actually solving the

problem. Remember equal number of variables and equations ensures a solution.

Is a > b ?

(1) a/b = 7/10

(2) a = 70/100*b
==> transforming the original condition and the question using variable approach method, we have 2 variables (a,b) and in order to match the number of variables and equations we need 2 equations. Since there is 1 each in 1) and 2), C is likely the answer.

Using both 1) & 2) together, the answer is yes if a=-7, b=10, while the answer is no if a=7, b=10. Since the conditions and not suffiicent. the answer is E
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Is a > b ?   [#permalink] 04 Sep 2015, 03:45
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