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# Is |a^2-b^2|<10?

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Math Revolution GMAT Instructor
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14 Jul 2016, 20:34
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Is |a^2-b^2|<10?
1) |a-b|<5
2) |a+b|<2

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[Reveal] Spoiler: OA

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Re: Is |a^2-b^2|<10? [#permalink]

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14 Jul 2016, 21:45
1
KUDOS
My Answer is C)

Below is my explanation, Please feel free to correct me, if wrong.
given |(a+b)(a-b)| < 10 --> A

a) |a-b| < 5
Let a = 10 , b = 7 : Above eq A is not satisfied
a = 3 , b = -2 : Above eq A is satisfied
Therefore, Not Suff.

b) |a+b| <2
If a = 1, b = 1/2 : Eq A is satisfied
a = 10 , b = -9 : Eq A is not satisfied.
Therefore, Not Suff.

a + b => Sufficient. Hence, C
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Re: Is |a^2-b^2|<10? [#permalink]

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18 Jul 2016, 08:16
Since there are 2 variables in the original condition, the correct answer is C.

- 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 independent equations ensures a solution.
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Re: Is |a^2-b^2|<10? [#permalink]

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19 Jul 2016, 00:55
Could I seperate the equation |(a+b)(a-b)|<10 as |a+b|*|a-b|<10?
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19 Jul 2016, 02:44
tinalongmao wrote:
Could I seperate the equation |(a+b)(a-b)|<10 as |a+b|*|a-b|<10?

Yes, you could.

Remember, Product and Division in absolute values could be separated.

I mean if we have |a/b|, we can write it as |a|/|b|

or |a*b|=|a|*|b|

-- Hit Kudos if you get the answer.
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Re: Is |a^2-b^2|<10? [#permalink]

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11 Aug 2017, 20:32
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

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Re: Is |a^2-b^2|<10?   [#permalink] 11 Aug 2017, 20:32
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# Is |a^2-b^2|<10?

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