NEW HERE? LEARN MORE
closeclose
Last visit was: 24 Apr 2024, 10:07 It is currently 24 Apr 2024, 10:07
Decision Tracker
My Rewards
New posts
New comers' posts

Close
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
Your Progress

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.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel

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

SORT BY:
Date
Kudos
Tags:
Find Similar Topics 
Show Tags
Hide Tags
avatar
sagarag
Intern
Intern
Joined: 13 May 2014
Posts: 16
Own Kudos [?]: 59 [18]
Given Kudos: 43
Schools: IIMA ISB '17 IIMC IIM Indore'17 IIMB
GMAT Date: 11-01-2014
Send PM
If x# = x(x + 3), what is the value of x## [#permalink] New post   12 Jan 2015, 07:55
1
Kudos
17
Bookmarks
00:00
A
B
C
D
E

Difficulty:

45% (medium)

Question Stats:

63% (01:25) correct 37% (01:39) wrong based on 296 sessions
Hide Show timer Statistics
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)
ShowHide Answer
Official Answer
C
Most Helpful Reply
User avatar
L
EMPOWERgmatRichC
GMAT Club Legend
GMAT Club Legend
Joined: 19 Dec 2014
Status:GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Posts: 21846
Own Kudos [?]: 11665 [6]
Given Kudos: 450
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Send PM
Re: If x# = x(x + 3), what is the value of x## [#permalink] New post   12 Jan 2015, 16:13
3
Kudos
3
Bookmarks
Expert Reply
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:
Show Spoiler
C


GMAT assassins aren't born, they're made,
Rich
General Discussion
User avatar
manpreetsingh86
Manager
Manager
Joined: 13 Jun 2013
Posts: 223
Own Kudos [?]: 1046 [1]
Given Kudos: 14
Send PM
Re: If x# = x(x + 3), what is the value of x## [#permalink] New post   12 Jan 2015, 08:49
1
Bookmarks
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
avatar
PareshGmat
SVP
SVP
Joined: 27 Dec 2012
Status:The Best Or Nothing
Posts: 1562
Own Kudos [?]: 7208 [2]
Given Kudos: 193
Location: India
Concentration: General Management, Technology
WE:Information Technology (Computer Software)
Send PM
If x# = x(x + 3), what is the value of x## [#permalink] New post   12 Jan 2015, 23:47
2
Kudos
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

\(X\#\# = x(x+3)[x(x+3) + 3] = x(x+3)(x^2 + 3x + 3)\)
User avatar
B
ranaazad
Manager
Manager
Joined: 16 Jan 2013
Posts: 66
Own Kudos [?]: 21 [0]
Given Kudos: 1323
Location: Bangladesh
GMAT 1: 490 Q41 V18
GMAT 2: 610 Q45 V28
GPA: 2.75
Send PM
If x# = x(x + 3), what is the value of x## [#permalink] New post   11 Jul 2016, 02:07
I don't understand the motif of this question. Nowhere does it ask to put x(x+3) in place of x.
User avatar
L
EMPOWERgmatRichC
GMAT Club Legend
GMAT Club Legend
Joined: 19 Dec 2014
Status:GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Posts: 21846
Own Kudos [?]: 11665 [2]
Given Kudos: 450
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Send PM
Re: If x# = x(x + 3), what is the value of x## [#permalink] New post   11 Jul 2016, 07:54
1
Kudos
1
Bookmarks
Expert Reply
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
User avatar
B
ranaazad
Manager
Manager
Joined: 16 Jan 2013
Posts: 66
Own Kudos [?]: 21 [0]
Given Kudos: 1323
Location: Bangladesh
GMAT 1: 490 Q41 V18
GMAT 2: 610 Q45 V28
GPA: 2.75
Send PM
Re: If x# = x(x + 3), what is the value of x## [#permalink] New post   11 Jul 2016, 08:01
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 :)
+1
User avatar
L
AkshdeepS
VP
VP
Joined: 13 Apr 2013
Status:It's near - I can see.
Posts: 1479
Own Kudos [?]: 1600 [0]
Given Kudos: 1002
Location: India
Concentration: International Business, Operations
GPA: 3.01
WE:Engineering (Real Estate)
Send PM
Reviews Badge
Re: If x# = x(x + 3), what is the value of x## [#permalink] New post   24 Apr 2019, 07:31
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)


Tricky :

Let us get it stepwise ;

Question : X## = ?

Break it : (X#)#

Solve the bracket part first:

X# = x(x+3)

Now , (X#)# = x(x+3) [x(x+3)+3]

x(x+3)(x^2+3x+3)

(C)
User avatar
G
RusskiyLev
Manager
Manager
Joined: 26 Mar 2019
Posts: 69
Own Kudos [?]: 104 [0]
Given Kudos: 142
Location: Azerbaijan
Concentration: Finance, Strategy
Schools: Booth '23 (II)
GMAT 1: 730 Q50 V38
Send PM
Reviews Badge
Re: If x# = x(x + 3), what is the value of x## [#permalink] New post   17 Jul 2019, 10:51
EMPOWERgmatRichC wrote:
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:
Show Spoiler
C


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


If we use 1 instead of 2, then X# = X (X + 3) = 1 * (1 + 3) = 1 * 4 = 4
In this case, X## = 4# = 4 * (4 + 3) = 4 * 7 = 28

Checking option C: X## = X (X + 3) (X^2 + 3X + 3) = 4 * (1^2 + 3 * 1 + 3) = 4 * 7 = 28
Checking option E: X## = X (X + 3) (X + 6X) = 4 * (1 + 6 * 1) = 4 * (1 + 6) = 4 * 7 = 28

In this case 2 options are suitable as you can see from an example above. What is your advice for this case?
User avatar
L
EMPOWERgmatRichC
GMAT Club Legend
GMAT Club Legend
Joined: 19 Dec 2014
Status:GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Posts: 21846
Own Kudos [?]: 11665 [0]
Given Kudos: 450
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Send PM
Re: If x# = x(x + 3), what is the value of x## [#permalink] New post   17 Jul 2019, 21:26
Expert Reply
Hi RusskiyLev,

When dealing with a PS question - and you're TESTing VALUES - it's generally a good idea to NOT use 0 or 1. You've actually discovered the big reason why with your example: more than one answer appears to be correct. Here, one of those 2 answers IS the correct one - so if you were low on time, then you could take a guess (knowing that it's a 50/50 shot). However, if you had started with a small number that is NOT 0 or 1 (in my explanation, I used X=2), then you can get the correct answer on the first try.

It's worth noting that some PS questions (for example, certain Number Property questions) are designed so that you'll have to do a little more work to get to the correct answer - so having more than one answer 'match' what you're looking for isn't necessary a bad outcome (it might be a built-in part of how the question was written).

GMAT assassins aren't born, they're made,
Rich
avatar
G
kitipriyanka
Manager
Manager
Joined: 26 Jan 2016
Posts: 101
Own Kudos [?]: 151 [0]
Given Kudos: 61
Send PM
Re: If x# = x(x + 3), what is the value of x## [#permalink] New post   17 Jul 2019, 23:10
Given: X# = x(x+3).....1
Find: X##?

Say X#=y
then y=x(x+3) ....2

now, we need to find y#
then replacing x in 1 with y
we get, y#=x(x+3)(x(x+3) +3)
y#= \(x(x+3)(x^2+3x+3)\)

Hence C
User avatar
L
kntombat
Retired Moderator
Joined: 28 Feb 2020
Posts: 949
Own Kudos [?]: 485 [0]
Given Kudos: 839
Location: India
WE:Other (Other)
Send PM
Re: If x# = x(x + 3), what is the value of x## [#permalink] New post   13 Oct 2020, 07:58
Bunuel, VeritasKarishma, chetan2u
Could either of you explain how to solve this question algebraically, I solved it using values but would love to know the algebraic approach also.

thanks.
User avatar
L
chetan2u
RC & DI Moderator
Joined: 02 Aug 2009
Status:Math and DI Expert
Posts: 11169
Own Kudos [?]: 31889 [1]
Given Kudos: 290
Send PM
Reviews Badge
Re: If x# = x(x + 3), what is the value of x## [#permalink] New post   13 Oct 2020, 09:34
1
Kudos
Expert Reply
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)


Hi kntombat
Algebraic way would again be very simple.
In step II just substitute x(x+3) for x.
x#=x(x+3)....

Step I :
x##=(x#)#=(x(x+3))#
Step II
Now substitute x as x(x+3)
So (x(x+3))#=(x(x+3))(x(x+3)+3)=x(x+3)(x^2+3x+3)

C
User avatar
bumpbot
Non-Human User
Joined: 09 Sep 2013
Posts: 32647
Own Kudos [?]: 821 [0]
Given Kudos: 0
Send PM
Re: If x# = x(x + 3), what is the value of x## [#permalink] New post   01 Jan 2022, 04:58
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
GMAT Club Bot
gmatclubot
Re: If x# = x(x + 3), what is the value of x## [#permalink]
01 Jan 2022, 04:58
Moderators:
Bunuel
Math Expert
92902 posts
yashikaaggarwal
Senior Moderator - Masters Forum
3137 posts

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne
Main navigation
GMAT Resources
Partners
MBA Resources
www.gmac.com|www.mba.com | | GMAT Club Rules | Terms and Conditions