GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 13 Dec 2019, 13:31 ### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

#### Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.  # If the expression x^2 – xy/5 + 25 can be expressed by (x – 5)^2, what

Author Message
TAGS:

### Hide Tags

Math Expert V
Joined: 02 Sep 2009
Posts: 59721
If the expression x^2 – xy/5 + 25 can be expressed by (x – 5)^2, what  [#permalink]

### Show Tags 00:00

Difficulty:   15% (low)

Question Stats: 83% (01:13) correct 17% (01:26) wrong based on 70 sessions

### HideShow timer Statistics

If the expression x^2 – xy/5 + 25 can be expressed by (x – 5)^2, what is the value of y?

(A) 0
(B) 5
(C) 25
(D) 50
(E) 5/x

_________________
Intern  B
Joined: 17 May 2016
Posts: 17
Re: If the expression x^2 – xy/5 + 25 can be expressed by (x – 5)^2, what  [#permalink]

### Show Tags

xy/5 = 10x
y = 10 x 5 = 50

Sent from my HM NOTE 1LTE using Tapatalk
Target Test Prep Representative G
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2809
Re: If the expression x^2 – xy/5 + 25 can be expressed by (x – 5)^2, what  [#permalink]

### Show Tags

1
1
Bunuel wrote:
If the expression x^2 – xy/5 + 25 can be expressed by (x – 5)^2, what is the value of y?

(A) 0
(B) 5
(C) 25
(D) 50
(E) 5/x

We can FOIL the second expression (x – 5)^2 and equate the two expressions:

x^2 – xy/5 + 25 = x^2 -10x + 25

-xy/5 = -10x

-xy = -50x

y = 50

_________________

# Jeffrey Miller

Jeff@TargetTestPrep.com

See why Target Test Prep is the top rated GMAT quant course on GMAT Club. Read Our Reviews

If you find one of my posts helpful, please take a moment to click on the "Kudos" button.

Intern  B
Joined: 14 Apr 2017
Posts: 6
Re: If the expression x^2 – xy/5 + 25 can be expressed by (x – 5)^2, what  [#permalink]

### Show Tags

Here y can take any value if x equals 0 and the question does not state that x is not equal to 0. In that consideration, shouldn't the answer be "Cannot be determined"? I think the answer should be D (i.e.: y=50) only if the question explicitly mentions that x does not equal 0.
Retired Moderator P
Joined: 22 Aug 2013
Posts: 1409
Location: India
Re: If the expression x^2 – xy/5 + 25 can be expressed by (x – 5)^2, what  [#permalink]

### Show Tags

mazhar7624 wrote:
Here y can take any value if x equals 0 and the question does not state that x is not equal to 0. In that consideration, shouldn't the answer be "Cannot be determined"? I think the answer should be D (i.e.: y=50) only if the question explicitly mentions that x does not equal 0.

But when it says x^2 - xy/5 + 25 = (x-5)^2

it means this expression is true for ALL values of x and y. So we have to generalise by the means of expanding (x-5)^2 and equating it with x^2 - xy/5 + 25
We cannot take a lone case of x=0.
EMPOWERgmat Instructor V
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 15725
Location: United States (CA)
GMAT 1: 800 Q51 V49 GRE 1: Q170 V170 Re: If the expression x^2 – xy/5 + 25 can be expressed by (x – 5)^2, what  [#permalink]

### Show Tags

Hi All,

We're told that X^2 - (X)(Y)/5 + 25 can be expressed as (X - 5)^2. We're asked for the value of Y. In simple terms, this question asks what value of Y will make the first expression be equal to the second expression.

(X - 5)^2 = X^2 - 10X + 25

Both the "X^2" and the "+25" are accounted for in the first expression, so we need -(X)(Y)/5 to equal - 10X....
thus Y/5 = 10
Y = 50

GMAT assassins aren't born, they're made,
Rich
_________________ Re: If the expression x^2 – xy/5 + 25 can be expressed by (x – 5)^2, what   [#permalink] 30 Nov 2019, 12:30
Display posts from previous: Sort by

# If the expression x^2 – xy/5 + 25 can be expressed by (x – 5)^2, what  