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# If x is positive, what is the value of y ?

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Study Buddy Forum Moderator
Joined: 04 Sep 2016
Posts: 1195
Location: India
WE: Engineering (Other)
If x is positive, what is the value of y ?  [#permalink]

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23 May 2018, 18:40
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5% (low)

Question Stats:

96% (00:35) correct 4% (00:25) wrong based on 69 sessions

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If x is positive, what is the value of y ?

(1) 5x = 15
(2) xy + y = 18

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Math Expert
Joined: 02 Sep 2009
Posts: 49254
If x is positive, what is the value of y ?  [#permalink]

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23 May 2018, 21:56
1
If x is positive, what is the value of y ?

(1) 5x = 15 --> x = 3. We know nothing about y. Not sufficient.#

(2) xy + y = 18. Infinitely many pairs of (x, y) satisfy this. For example, x = 1 and y = 9; x = 2 and y = 6; ... Not sufficient.

(1)+(2) Since x = 3 from (1), then y = 18/4 from (2). Sufficient.

P.S. Is this a new question from GMAT Prep?
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Study Buddy Forum Moderator
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WE: Engineering (Other)
Re: If x is positive, what is the value of y ?  [#permalink]

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24 May 2018, 01:27
1
Bunuel

Yes, this is from New Gmat prep version.
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Joined: 26 Apr 2018
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Re: If x is positive, what is the value of y ?  [#permalink]

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05 Jun 2018, 12:06
When you plug 3 back into 3y + y = 18, why does it not equal 18? I got the question right on my mock, I just want to keep from getting confused. Is it just the fact that we COULD solve for y?
DS Forum Moderator
Joined: 22 Aug 2013
Posts: 1343
Location: India
Re: If x is positive, what is the value of y ?  [#permalink]

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05 Jun 2018, 21:02
1
tripledown wrote:
When you plug 3 back into 3y + y = 18, why does it not equal 18? I got the question right on my mock, I just want to keep from getting confused. Is it just the fact that we COULD solve for y?

Hello

Yes, its the fact that we can solve for y and get a unique value of y - that combined the two statements are sufficient to answer the question. Thats why the answer is C.
Value of y is immaterial but still: 3y+y = 18 means y = 18/4.
Manager
Joined: 10 Apr 2018
Posts: 95
Re: If x is positive, what is the value of y ?  [#permalink]

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05 Sep 2018, 00:52
Bunuel wrote:
If x is positive, what is the value of y ?

(1) 5x = 15 --> x = 3. We know nothing about y. Not sufficient.#

(2) xy + y = 18. Infinitely many pairs of (x, y) satisfy this. For example, x = 1 and y = 9; x = 2 and y = 6; ... Not sufficient.

(1)+(2) Since x = 3 from (1), then y = 3 from (2). Sufficient.

P.S. Is this a new question from GMAT Prep?

Hi Bunuel,
I am getting a different answer for y. Can you help me understand why
x= 3
the y(x+1)=18
then
y(4)=18
then y= $$\frac{18}{4}$$
Math Expert
Joined: 02 Sep 2009
Posts: 49254
Re: If x is positive, what is the value of y ?  [#permalink]

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05 Sep 2018, 00:56
Probus wrote:
Bunuel wrote:
If x is positive, what is the value of y ?

(1) 5x = 15 --> x = 3. We know nothing about y. Not sufficient.#

(2) xy + y = 18. Infinitely many pairs of (x, y) satisfy this. For example, x = 1 and y = 9; x = 2 and y = 6; ... Not sufficient.

(1)+(2) Since x = 3 from (1), then y = 3 from (2). Sufficient.

P.S. Is this a new question from GMAT Prep?

Hi Bunuel,
I am getting a different answer for y. Can you help me understand why
x= 3
the y(x+1)=18
then
y(4)=18
then y= $$\frac{18}{4}$$

Yes, you are right. Edited the typo. Thank you.
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Re: If x is positive, what is the value of y ? &nbs [#permalink] 05 Sep 2018, 00:56
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