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Is a=b?

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Is a=b? [#permalink]

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New post 10 Jul 2016, 23:50
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Is a=b?
1) a^2=b^2
2) a=1

*An answer will be posted in 2 days
[Reveal] Spoiler: OA

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Is a=b? [#permalink]

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New post 11 Jul 2016, 02:10
MathRevolution wrote:
Is a=b?
1) a^2=b^2
2) a=1

*An answer will be posted in 2 days



Given to find if a=b?

Stat 1 : \(a^2\) = \(b^2\).

Here a or b can be positive or negative, when we square negative or positive we get the same result.

For ex:
if a = -2 or b = 2. Upon squaring we get both same result i.e. 4. But a is -2 , b is +2. Here a is not equal to b.

if a = 2 or b = 2. Upon squaring we get both same result i.e. 4. But a is +2 , b is +2. Here a = b .

Two different cases. Insufficient.

Stat 2 : Given only about a = 1, but we are not sure about the value of b if it a positive or negative or what it is. Insufficient.

Stat 1 + Stat 2 : If a = 1 ( from stat 2).
Substitute in Stat 1 => 1 = \(b^2\). Now here b will get 1 or -1. There is no unique value. Thus both stats insufficient.

Correct option is E.

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Re: Is a=b? [#permalink]

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New post 11 Jul 2016, 17:24
There are 2 variables in the original condition. In order to match the number of variables and the number of equations, we need 2 equations. There is a high chance that C is the correct answer. Using 1) & 2), from a=1 and b=-1, 1, the answer is both yes or no. Hence, the conditions are not sufficient and the correct answer is E.

- 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=b? [#permalink]

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New post 11 Jul 2016, 18:17
MathRevolution wrote:
Is a=b?
1) a^2=b^2
2) a=1

*An answer will be posted in 2 days

(1)
sq. root both sides then
IaI=IbI
a and b can be positive or negative having same magnitude(distance from 0)
Not suff...
(2)a=1
No info on b ..
Not suff..
Combining (1) & (2)
if a=1 then b=1 or -1
Not suff....
Ans E

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Re: Is a=b? [#permalink]

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New post 04 Sep 2016, 01:35
Please move this question to DS section
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Re: Is a=b? [#permalink]

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New post 03 Aug 2017, 09:05
Needed : Is \(a = b?\)

S1: \(a^2 = b^2\)

=> \(a^2 - b^2 = 0\)

=> \((a-b)(a+b) = 0\)

=> \(a = b\) or \(a=-b\)

Insuff

S2: \(a = 1\). No information on b. Clearly insuff

S1+S2: \(1^2 = b^2\)

if \(b = 1\), \(a = b\) IF \(b=-1\), \(a ≠ b\)

Both statements together insuff. Final answer E
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Re: Is a=b?   [#permalink] 03 Aug 2017, 09:05
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