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# if X# = x(x+3), what is the value of X##

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Intern
Joined: 13 May 2014
Posts: 25
GMAT Date: 11-01-2014
if X# = x(x+3), what is the value of X##  [#permalink]

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12 Jan 2015, 07:55
6
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Difficulty:

35% (medium)

Question Stats:

67% (00:55) correct 33% (01:13) wrong based on 177 sessions

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if X# = x(x+3), what is the value of X##

A) x(x+3)
B) (x(x+3))^2
C) x(x+3)(x^2+3x+3)
D) x(x+3)(x+4x)
E) x(x+3)(x+6x)
Senior Manager
Joined: 13 Jun 2013
Posts: 277
Re: if X# = x(x+3), what is the value of X##  [#permalink]

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12 Jan 2015, 08:49
sagarag wrote:
if X# = x(x+3), what is the value of X##

A) x(x+3)
B) [x(x+3)]^2
C) x(x+3)(x^2+3x+3)
D) x(x+3)(x+4x)
E) x(x+3)(x+6x)

X# = x(x+3)----------------------------1)

now while computing X## , we will put x(x+3) in place of x in equation 1.

thus,
X## = x(x+3)(x(x+3)+3)
=x(x+3)(x^2+3x+3)

which is option C
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Re: if X# = x(x+3), what is the value of X##  [#permalink]

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12 Jan 2015, 16:13
2
2
Hi sagarag,

This is an example of "Symbolism" question. We're given a symbol, told what it represents mathematically, then asked to perform a calculation with it. Since we're not given any specific values to work with, we can TEST VALUES.

We're told that X# = X(X+3)

eg
2# = 2(2+3) = 10

We're asked for the value of X##.....notice the second symbol - this means that we have to perform TWO calculations using this Symbol (the RESULT of the first calculation gets put back into the Symbol to get us the second, final result).

IF...X = 2
2## = 2(2+3) = 10
10# = 10(10+3) = 130

So we're looking for an answer that = 130 when X = 2

While these answers look "crazy", notice what they ALL have in common....X(X+3)....We do NOT have to do THAT calculation 5 times; we just have to do it ONCE and plug the result into all 5 answers.

Answer A: 10 is NOT a match
Answer B: 10^2 = 100 is NOT a match
Answer C: 10(13) = 130 IS a MATCH
Answer D: 10(10) = 100 is NOT a match
Answer E: 10(14) = 140 is NOT a match

GMAT assassins aren't born, they're made,
Rich
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Special Offer: Save $75 + GMAT Club Tests Free Official GMAT Exam Packs + 70 Pt. Improvement Guarantee www.empowergmat.com/ ***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!*********************** SVP Status: The Best Or Nothing Joined: 27 Dec 2012 Posts: 1834 Location: India Concentration: General Management, Technology WE: Information Technology (Computer Software) Re: if X# = x(x+3), what is the value of X## [#permalink] ### Show Tags 12 Jan 2015, 23:47 Answer = C) x(x+3)(x^2+3x+3) X# = x(x+3) To find the value of X##, place x(x+3) in the place of x $$X## = x(x+3)[x(x+3) + 3] = x(x+3)(x^2 + 3x + 3)$$ _________________ Kindly press "+1 Kudos" to appreciate Manager Joined: 16 Jan 2013 Posts: 88 Location: Bangladesh GMAT 1: 490 Q41 V18 GMAT 2: 610 Q45 V28 GPA: 2.75 Re: if X# = x(x+3), what is the value of X## [#permalink] ### Show Tags 11 Jul 2016, 02:05 I don't understand the motif of this question. Nowhere does it ask to put x(x+3) in place of x. _________________ Heading towards perfection>> Math Expert Joined: 02 Sep 2009 Posts: 49327 Re: if X# = x(x+3), what is the value of X## [#permalink] ### Show Tags 11 Jul 2016, 02:07 ranaazad wrote: I don't understand the motif of this question. Nowhere does it ask to put x(x+3) in place of x. Have you read this: if-x-x-x-3-what-is-the-value-of-x-191507.html#p1468265 _________________ EMPOWERgmat Instructor Status: GMAT Assassin/Co-Founder Affiliations: EMPOWERgmat Joined: 19 Dec 2014 Posts: 12444 Location: United States (CA) GMAT 1: 800 Q51 V49 GRE 1: Q170 V170 Re: if X# = x(x+3), what is the value of X## [#permalink] ### Show Tags 11 Jul 2016, 07:54 1 Hi ranaazad, Symbolism questions sometimes ask you to use the given symbol/function more than once. Here, we're asked for the value of X##, which is the same as asking for the value of (X#)#. If you're going to approach this question algebraically, since X# = X(X+3), so you would then have to plug in "X(X+3)" into the symbol again (for the second part of the calculation) to answer the given question. You would likely find TESTing VALUES to be an easier approach. GMAT assassins aren't born, they're made, Rich _________________ 760+: Learn What GMAT Assassins Do to Score at the Highest Levels Contact Rich at: Rich.C@empowergmat.com # Rich Cohen Co-Founder & GMAT Assassin Special Offer: Save$75 + GMAT Club Tests Free
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Re: if X# = x(x+3), what is the value of X##  [#permalink]

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11 Jul 2016, 08:01
EMPOWERgmatRichC wrote:

Symbolism questions sometimes ask you to use the given symbol/function more than once. Here, we're asked for the value of X##, which is the same as asking for the value of (X#)#. If you're going to approach this question algebraically, since X# = X(X+3), so you would then have to plug in "X(X+3)" into the symbol again (for the second part of the calculation) to answer the given question. You would likely find TESTing VALUES to be an easier approach.

GMAT assassins aren't born, they're made,
Rich

I started in the algebraic way and ended up nowhere because I didn't understand what the question was asking. Thank you for making it clear now
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Re: if X# = x(x+3), what is the value of X##  [#permalink]

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08 Sep 2018, 13:04
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