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555-605 (Medium)|   Algebra|      
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flower07
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What is y? 13 Dec 2013, 16:31
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E
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

Difficulty:

25% (medium)

Question Stats:

69% (01:05) correct 31% (00:51) wrong based on 272 sessions

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Time
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What is y?

(1) x - y = 1
(2) xy = 12

I understand the question but my doubt however is:
Show Spoiler
The MGMAT Guide says,
Quote:
Even when the equations are combined, they do not provide enough information to find y, and the
answer is (E).
Show more
. I do not understand why it says that because when I combine both the equations, I get a quadratic equation. I solve it and I get two answers y = -4 or y = 3. So, my take is using both the equations I am able to find the value of y. So, why is the correct answer E and why not C? Thank you!
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E
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Bunuel
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What is y? 14 Dec 2013, 06:12
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flower07
What is y?

(1) x - y = 1
(2) xy = 12

I understand the question but my doubt however is:

The MGMAT Guide says,
Quote:
Even when the equations are combined, they do not provide enough information to find y, and the
answer is (E).
. I do not understand why it says that because when I combine both the equations, I get a quadratic equation. I solve it and I get two answers y = -4 or y = 3. So, my take is using both the equations I am able to find the value of y. So, why is the correct answer E and why not C? Thank you!
Show more

When a DS question asks about the value of some variable, then the statement is sufficient ONLY if you can get the single numerical value of this variable.

Since you get TWO possible values of y, the statements are not sufficient.

Hope it's clear.
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tuanle
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What is y? 14 Dec 2013, 04:36
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flower07
What is y?

(1) x - y = 1
(2)x y = 12

I understand the question but my doubt however is:
Show Spoiler
The MGMAT Guide says,
Quote:
Even when the equations are combined, they do not provide enough information to find y, and the
answer is (E).
. I do not understand why it says that because when I combine both the equations, I get a quadratic equation. I solve it and I get two answers y = -4 or y = 3. So, my take is using both the equations I am able to find the value of y. So, why is the correct answer E and why not C? Thank you!
Show more
You got two possible values of y, which means that you don't know which one must be y (only one value counted!). The answer should be E
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sahilchaudhary
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What is y? 14 Dec 2013, 11:01
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I marked E since we are getting 2 values of y(3,-4) even after combining both the equations.
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Nunuboy1994
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What is y? 24 May 2017, 12:33
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flower07
What is y?

(1) x - y = 1
(2) xy = 12

I understand the question but my doubt however is:
Show Spoiler
The MGMAT Guide says,
Quote:
Even when the equations are combined, they do not provide enough information to find y, and the
answer is (E).
. I do not understand why it says that because when I combine both the equations, I get a quadratic equation. I solve it and I get two answers y = -4 or y = 3. So, my take is using both the equations I am able to find the value of y. So, why is the correct answer E and why not C? Thank you!
Show more

You just have to pay attention to the mild trap this question is baiting you into - it wants to make sure you are remembering the commutative instead of making assumptions. For example,

(4)3= 12
4-3 = 1

BUT

-3(-4)=12
-3 --4= 1
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Nunuboy1994
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What is y? 08 Sep 2017, 20:35
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flower07
What is y?

(1) x - y = 1
(2) xy = 12

I understand the question but my doubt however is:
Show Spoiler
The MGMAT Guide says,
Quote:
Even when the equations are combined, they do not provide enough information to find y, and the
answer is (E).
. I do not understand why it says that because when I combine both the equations, I get a quadratic equation. I solve it and I get two answers y = -4 or y = 3. So, my take is using both the equations I am able to find the value of y. So, why is the correct answer E and why not C? Thank you!
Show more

Nice trick here...classic "C" trap

St 1

x-y =1 - clearly too many possibilities

insuff

St 2

xy = 12

clearly too many possibilities

insuff


St 1 and St 2

This question wants you to assume that the answer should be 4 and 3...however the answer can also be -3 and -4


E
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What is y? 20 Jan 2022, 06:13
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