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# Is a=b?

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Math Revolution GMAT Instructor
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24 Feb 2017, 01:15
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78% (00:28) correct 22% (00:22) wrong based on 49 sessions

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Is a=b?

1) $$a^2=b^2$$
2) $$a=2$$
[Reveal] Spoiler: OA

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Last edited by Bunuel on 24 Feb 2017, 07:01, edited 1 time in total.
Edited the OA.
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24 Feb 2017, 02:48
(1) a^2 = b^2;
Suppose, a = 2, and b = 2, Therefore, a = b;

Again, suppose a= 2 and b = -2; In this case also a^2 = b^2 is true, but a ≠ b; Hence, Insufficient.

(2) a = 2; Insufficient;

(1) And (2) together, Insufficient;

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24 Feb 2017, 06:45
MathRevolution wrote:
Is a=b?

1) $$a^2=b^2$$
2) $$a=2$$

Hi Bunuel

Can throw some light on this question

Seems like ans is E. Can you validate.
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Joined: 24 Feb 2017
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24 Feb 2017, 06:50
MathRevolution wrote:
Is a=b?

1) $$a^2=b^2$$
2) $$a=2$$

In statement 1, If a^2 = b^2, then b can be equal to a or b can be equal to -a because a^2 is also equal to (-a)^2. Hence insufficient
In statement 2, a = 2, but there is no information of b. Hence, insufficient

By combining, if a = 2, then a^2 is 4. But b can be 2 or -2 because 2^2 = 4 and (-2)^2 is also 4.

Hence, together also insufficient.

Thanks,
Anant Saraogi
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Joined: 11 Sep 2015
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24 Feb 2017, 06:53
Expert's post
Top Contributor
NandishSS wrote:
MathRevolution wrote:
Is a=b?

1) $$a^2=b^2$$
2) $$a=2$$

Hi Bunuel

Can throw some light on this question

Seems like ans is E. Can you validate.

You're right; the correct answer is E

Statements 1 and 2 combined
Case a: a = 2 and b = 2, in which case a EQUALS b
Case b: a = 2 and b = -2, in which case a DOES NOT EQUAL b
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT

Cheers,
Brent
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24 Feb 2017, 17:34
GMATPrepNow wrote:
NandishSS wrote:
MathRevolution wrote:
Is a=b?

1) $$a^2=b^2$$
2) $$a=2$$

Hi Bunuel

Can throw some light on this question

Seems like ans is E. Can you validate.

You're right; the correct answer is E

Statements 1 and 2 combined
Case a: a = 2 and b = 2, in which case a EQUALS b
Case b: a = 2 and b = -2, in which case a DOES NOT EQUAL b
Since we cannot answer the target question with certainty, the combined statements are NOT SUFFICIENT

Cheers,
Brent

Thank you Brent

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26 Feb 2017, 20:32
==> In the original condition, there are 2 variables (a,b) and in order to match the number of variables to the number of equations, there must be 2 equations. Since there is 1 for con 1) and 1 for con 2), C is most likely to be the answer. By solving con 1) and con 2), from a=2, you get $$b^2=2^2=4$$, then b=±2. Thus, (a,b)=(2,2) yes but (a,b)=(2,-2) no, hence it is not sufficient.

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Re: Is a=b?   [#permalink] 26 Feb 2017, 20:32
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