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

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

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New post 12 Jan 2015, 06:55
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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)
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Re: if X# = x(x+3), what is the value of X##  [#permalink]

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New post 12 Jan 2015, 15:13
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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

Final Answer:

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

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New post 12 Jan 2015, 07:49
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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New post 12 Jan 2015, 22:47
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

\(X## = x(x+3)[x(x+3) + 3] = x(x+3)(x^2 + 3x + 3)\)
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Re: if X# = x(x+3), what is the value of X##  [#permalink]

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New post 11 Jul 2016, 01:05
I don't understand the motif of this question. Nowhere does it ask to put x(x+3) in place of x.
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Re: if X# = x(x+3), what is the value of X##  [#permalink]

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New post 11 Jul 2016, 01:07
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Re: if X# = x(x+3), what is the value of X##  [#permalink]

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New post 11 Jul 2016, 06:54
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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.

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

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New post 11 Jul 2016, 07:01
EMPOWERgmatRichC wrote:
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


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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