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# The variable x is inversely proportional to the square of the variable

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Intern
Joined: 20 May 2014
Posts: 12
The variable x is inversely proportional to the square of the variable [#permalink]

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18 Sep 2015, 19:04
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Question Stats:

59% (00:57) correct 41% (00:57) wrong based on 336 sessions

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The variable x is inversely proportional to the square of the variable y. If y is divided by 3a, then x is multiplied by which of the following?

a. 1/9a

b. 1/9a^2

c. 1/3a

d. 9a

e. 9a^2
[Reveal] Spoiler: OA
Manager
Joined: 23 Sep 2015
Posts: 90
Concentration: General Management, Finance
GMAT 1: 680 Q46 V38
GMAT 2: 690 Q47 V38
GPA: 3.5
Re: The variable x is inversely proportional to the square of the variable [#permalink]

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06 Nov 2015, 00:23
Tried this question

not sure how to set it up when the say inversely proportional

initially - did x= 1/y^2

But this yielded the wrong answer,

I then re examined the question and tried y^2/x =1

Which I then got y = SQR(X)

subbing into y/3a I got answer E)

not sure what is the correct way to do this. thanks!
Manager
Joined: 26 Nov 2014
Posts: 105
Re: The variable x is inversely proportional to the square of the variable [#permalink]

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07 Nov 2015, 07:11
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Let , $$x = k *\frac{1}{y^2}$$ , Where K is constant.

$$x = k * \frac{1}{(3a)^2}$$ = $$k * \frac{1}{9a^2}$$

=> $$k = (9a^2)x$$

Ans E.
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Intern
Joined: 21 Mar 2014
Posts: 39
Re: The variable x is inversely proportional to the square of the variable [#permalink]

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13 Dec 2015, 09:32
GMATDemiGod wrote:
Tried this question

not sure how to set it up when the say inversely proportional

initially - did x= 1/y^2

But this yielded the wrong answer,

I then re examined the question and tried y^2/x =1

Which I then got y = SQR(X)

subbing into y/3a I got answer E)

not sure what is the correct way to do this. thanks!

hi, u missed a point, y is divided by 3a, i.e y^2 is divided by 9a^2.....
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Intern
Joined: 21 Mar 2014
Posts: 39
Re: The variable x is inversely proportional to the square of the variable [#permalink]

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13 Dec 2015, 09:32
GMATDemiGod wrote:
Tried this question

not sure how to set it up when the say inversely proportional

initially - did x= 1/y^2

But this yielded the wrong answer,

I then re examined the question and tried y^2/x =1

Which I then got y = SQR(X)

subbing into y/3a I got answer E)

not sure what is the correct way to do this. thanks!

hi, u missed a point, y is divided by 3a, i.e y^2 is divided by 9a^2.....
_________________

kinaare paaon phailane lage hian,
nadi se roz mitti kat rahi hai....

Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 7988
Location: Pune, India
Re: The variable x is inversely proportional to the square of the variable [#permalink]

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04 Jan 2017, 06:32
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pmklings wrote:
The variable x is inversely proportional to the square of the variable y. If y is divided by 3a, then x is multiplied by which of the following?

a. 1/9a

b. 1/9a^2

c. 1/3a

d. 9a

e. 9a^2

Here is a post on inverse variation: the-variable-x-is-inversely-proportional-to-the-square-of-the-variable-205761.html

Now read the following:

x * y^2 = k

x' * (y/3a)^2 = k = x * y^2

x' * (y^2)/9a^2 = x * y^2

x' = x * 9a^2

Answer (E)
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Karishma
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Get started with Veritas Prep GMAT On Demand for $199 Veritas Prep Reviews Senior Manager Joined: 25 Mar 2013 Posts: 271 Location: United States Concentration: Entrepreneurship, Marketing GPA: 3.5 Re: The variable x is inversely proportional to the square of the variable [#permalink] ### Show Tags 18 Jan 2017, 15:42 VeritasPrepKarishma wrote: pmklings wrote: Here is a post on inverse variation: the-variable-x-is-inversely-proportional-to-the-square-of-the-variable-205761.html Now read the following: x * y^2 = k x' * (y/3a)^2 = k = x * y^2 x' * (y^2)/9a^2 = x * y^2 x' = x * 9a^2 Answer (E) Sorry I don't understand, Can anyone explain. Thanks The variable x is inversely proportional to the square of the variable y ??? Why x*y^2 ?? I wrote as $$\frac{1}{x}$$ = y^2 _________________ I welcome analysis on my posts and kudo +1 if helpful. It helps me to improve my craft.Thank you Intern Joined: 05 Aug 2012 Posts: 19 WE: Project Management (Pharmaceuticals and Biotech) Re: The variable x is inversely proportional to the square of the variable [#permalink] ### Show Tags 18 Jan 2017, 17:36 VeritasPrepKarishma wrote: VeritasPrepKarishma Did you man to post another link? This is the problem being discussed. Manager Joined: 22 May 2015 Posts: 100 Re: The variable x is inversely proportional to the square of the variable [#permalink] ### Show Tags 18 Jan 2017, 18:09 1 This post was BOOKMARKED Even i selected B as the answer. When the question says "x is multiplied by" it seems to ask for the constant that is multiplies X to keep the inverse proportion valid, but it really is asking for by what factor does the new value of X differ from the previous one which is Option E. xy^2 = K or X = K/y^2 Xy^2/9a = K => X(new) = 9a (K/y^2) from above = 9a(X(old)) = X(old) * 9a i.e X (new) = X(old) * 9a => Option E I have this problem of not understanding/misinterpreting the question sometimes :'( :'( _________________ Consistency is the Key Veritas Prep GMAT Instructor Joined: 16 Oct 2010 Posts: 7988 Location: Pune, India Re: The variable x is inversely proportional to the square of the variable [#permalink] ### Show Tags 19 Jan 2017, 00:56 raeann105 wrote: VeritasPrepKarishma wrote: VeritasPrepKarishma Did you man to post another link? This is the problem being discussed. Oops! Yes, it is this one: https://www.veritasprep.com/blog/2013/0 ... inversely/ _________________ Karishma Veritas Prep | GMAT Instructor My Blog Get started with Veritas Prep GMAT On Demand for$199

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Re: The variable x is inversely proportional to the square of the variable [#permalink]

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19 Jan 2017, 01:00
kanusha wrote:
VeritasPrepKarishma wrote:
pmklings wrote:

Here is a post on inverse variation: the-variable-x-is-inversely-proportional-to-the-square-of-the-variable-205761.html

Now read the following:

x * y^2 = k

x' * (y/3a)^2 = k = x * y^2

x' * (y^2)/9a^2 = x * y^2

x' = x * 9a^2

Answer (E)

Sorry I don't understand, Can anyone explain. Thanks
The variable x is inversely proportional to the square of the variable y ???
Why x*y^2 ??

I wrote as $$\frac{1}{x}$$ = y^2

You can write it as

k/x = y^2
which is the same as k = x * y^2

Note that it is not necessary that constant is 1. k could take any value. So when you equate, you need to use k, not 1.
Check out the post for which the link is given above.
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Manager
Joined: 17 May 2015
Posts: 211
Re: The variable x is inversely proportional to the square of the variable [#permalink]

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19 Jan 2017, 02:21
kanusha wrote:
VeritasPrepKarishma wrote:
pmklings wrote:

Here is a post on inverse variation: the-variable-x-is-inversely-proportional-to-the-square-of-the-variable-205761.html

Now read the following:

x * y^2 = k

x' * (y/3a)^2 = k = x * y^2

x' * (y^2)/9a^2 = x * y^2

x' = x * 9a^2

Answer (E)

Sorry I don't understand, Can anyone explain. Thanks
The variable x is inversely proportional to the square of the variable y ???
Why x*y^2 ??

I wrote as $$\frac{1}{x}$$ = y^2

Hi ,

The variable x is inversely proportional to the square of the variable y ???

The above statement can be written as follows:

$$x \propto \frac{1}{y^{2}} = \frac{k}{y^{2}}$$ , where $$k$$ is a proportionality constant.
or you can wtite it as
$$x y^{2} = k$$.

Hope this helps.
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Joined: 09 Sep 2013
Posts: 6532
Re: The variable x is inversely proportional to the square of the variable [#permalink]

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02 Mar 2018, 17:54
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Re: The variable x is inversely proportional to the square of the variable   [#permalink] 02 Mar 2018, 17:54
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# The variable x is inversely proportional to the square of the variable

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