If # represents one of the operations +,- and *, is a # : GMAT Data Sufficiency (DS)
Check GMAT Club App Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

It is currently 10 Dec 2016, 22:05
GMAT Club Tests

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.

Close

Request Expert Reply

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

If # represents one of the operations +,- and *, is a #

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Manager
Manager
avatar
Joined: 16 Feb 2010
Posts: 225
Followers: 2

Kudos [?]: 277 [0], given: 16

If # represents one of the operations +,- and *, is a # [#permalink]

Show Tags

New post 19 Sep 2010, 14:49
1
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  25% (medium)

Question Stats:

72% (01:54) correct 28% (01:21) wrong based on 213 sessions

HideShow timer Statistics

If # represents one of the operations +,- and *, is a # (b-c) = (a#b) – (a#c) for all numbers a, b and c.

(1) a#1 is not equal to 1#a for some numbers a

(2) # represents subtraction
[Reveal] Spoiler: OA

Last edited by zisis on 19 Sep 2010, 15:09, edited 1 time in total.
1 KUDOS received
Manager
Manager
avatar
Joined: 23 Sep 2009
Posts: 151
Followers: 1

Kudos [?]: 95 [1] , given: 37

Re: If # represents one of the operations +,- and *, is a # [#permalink]

Show Tags

New post 19 Sep 2010, 15:50
1
This post received
KUDOS
zisis wrote:
If # represents one of the operations +,- and *, is a # (b-c) = (a#b) – (a#c) for all numbers a, b and c.

(1) a#1 is not equal to 1#a for some numbers a

(2) # represents subtraction



Mods, please to DS section...posted by mistake in PS - apologies


1. From choice 1 it is clear that # is subtraction. coz a+1=1+1, a*1=1*a but a-1!=(not equal) 1-a.
2. Choice 2 says directly that it is subtraction.

Hence answer is D
_________________

Thanks,
VP

Senior Manager
Senior Manager
avatar
Joined: 20 Jul 2010
Posts: 269
Followers: 2

Kudos [?]: 75 [0], given: 9

GMAT ToolKit User Reviews Badge
Re: If # represents one of the operations +,- and *, is a # [#permalink]

Show Tags

New post 19 Sep 2010, 14:58
I converted question to 3 euqations where # can be +, - or *

So
I) When # = *
ab-ac = ab-ac (true for all values)

II) When # = +
Is a+b-c=b-c

III) When #=-
Is a-b+c = -b-c?

With option A we know # is not * as 1*a is always equal to a*1. So given equation is not equal
With option B , equation is not equal.

So answer choice D
_________________

If you like my post, consider giving me some KUDOS !!!!! Like you I need them

Intern
Intern
User avatar
Joined: 27 Jul 2010
Posts: 20
Location: Bangalore
Followers: 0

Kudos [?]: 4 [0], given: 0

Re: If # represents one of the operations +,- and *, is a # [#permalink]

Show Tags

New post 19 Sep 2010, 18:38
vigneshpandi wrote:
zisis wrote:
If # represents one of the operations +,- and *, is a # (b-c) = (a#b) – (a#c) for all numbers a, b and c.

(1) a#1 is not equal to 1#a for some numbers a

(2) # represents subtraction



Mods, please to DS section...posted by mistake in PS - apologies


1. From choice 1 it is clear that # is subtraction. coz a+1=1+1, a*1=1*a but a-1!=(not equal) 1-a.
2. Choice 2 says directly that it is subtraction.

Hence answer is D



IMO, it cannot be "not equal" always.

If # is subtraction,

a#(b-c)=a-(b-c)=a-b+c

(a#b)-(a#c)=(a-b)-(a-c)=a-b-a+c=-b+c

a-b+c=-b+c when a=0 and not equal for other values.. So both are insufficient.. Am I missing something here?
_________________

Nothing is free.. You 've to earn it!!!

Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 35951
Followers: 6867

Kudos [?]: 90123 [0], given: 10418

Re: If # represents one of the operations +,- and *, is a # [#permalink]

Show Tags

New post 19 Sep 2010, 23:14
BalakumaranP wrote:
IMO, it cannot be "not equal" always.

If # is subtraction,

a#(b-c)=a-(b-c)=a-b+c

(a#b)-(a#c)=(a-b)-(a-c)=a-b-a+c=-b+c

a-b+c=-b+c when a=0 and not equal for other values.. So both are insufficient.. Am I missing something here?


If # represents one of the operations +, - and *, is \(a#(b-c)=(a#b)-(a#c)\) for all numbers \(a\), \(b\) and \(c\).

(1) \(a#1\) is not equal to \(1#a\) for some numbers \(a\).

\(#\) is neither addition (as \(a+1=1+a\)) not multiplication (as \(a*1=1*a\)), so \(#\) is a subtraction. Then \(LHS=a#(b-c)=a-b+c\) and \(RHS=(a#b)-(a#c)=(a-b)-(a-c)=c-b\), so the question becomes "is \(a-b+c=c-b\) for all numbers \(a\), \(b\) and \(c\)?" --> "is \(a=0\)". So when \(a=0\) (and \(#\) is a subtraction) then \(a#(b-c)=(a#b)-(a#c)\) holds true but not for other values of \(a\), so not for all numbers \(a\), \(b\) and \(c\). Answer to the question is NO. Sufficient.

(2) \(#\) represents subtraction --> the same as above. Sufficient.

Answer: D.

Hope it's clear.
_________________

New to the Math Forum?
Please read this: All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Intern
Intern
User avatar
Joined: 27 Jul 2010
Posts: 20
Location: Bangalore
Followers: 0

Kudos [?]: 4 [0], given: 0

Re: If # represents one of the operations +,- and *, is a # [#permalink]

Show Tags

New post 20 Sep 2010, 02:09
Okay.. I read the question wrong...
_________________

Nothing is free.. You 've to earn it!!!

Manager
Manager
avatar
Joined: 04 Aug 2010
Posts: 158
Followers: 2

Kudos [?]: 27 [0], given: 15

Re: If # represents one of the operations +,- and *, is a # [#permalink]

Show Tags

New post 20 Sep 2010, 18:10
(1) a#1 is not equal to 1#a for some numbers a

a + 1 = 1 + a for all a
a*1 = 1*a for all a

a - 1 != 1 - a

Statement (1) implies # is a minus sign, so it has same meaning as (2).

Ans D
Manager
Manager
avatar
Joined: 06 Aug 2010
Posts: 225
Location: Boston
Followers: 3

Kudos [?]: 177 [0], given: 5

Re: If # represents one of the operations +,- and *, is a # [#permalink]

Show Tags

New post 21 Sep 2010, 09:55
zisis wrote:
If # represents one of the operations +,- and *, is a # (b-c) = (a#b) – (a#c) for all numbers a, b and c.

(1) a#1 is not equal to 1#a for some numbers a

(2) # represents subtraction



Mods, please to DS section...posted by mistake in PS - apologies


You're told that "#" is either addition, subtraction, or multiplication, and then asked if "#" satisfies the distributive property. Of these three, distribution only holds for multiplication, so if "#" is "*", it holds, and if "#" isn't "*", then it does not hold.

All we really need to know is what operation "#" really is.

(1) This is only true of subtraction, so # is subtraction and the distributive property does not hold. Sufficient.
(2) Same as above. Sufficient.

(D)
Verbal Forum Moderator
Verbal Forum Moderator
User avatar
Joined: 29 Apr 2015
Posts: 899
Location: Switzerland
Concentration: Economics, Finance
Schools: LBS MIF '19
WE: Asset Management (Investment Banking)
Followers: 50

Kudos [?]: 1168 [0], given: 302

GMAT ToolKit User Premium Member
Re: If # represents one of the operations +,- and *, is a # [#permalink]

Show Tags

New post 03 Jun 2015, 07:54
zisis wrote:
If # represents one of the operations +,- and *, is a # (b-c) = (a#b) – (a#c) for all numbers a, b and c.

(1) a#1 is not equal to 1#a for some numbers a

(2) # represents subtraction


Could someone edit this question so it will be an actual question? There is no proper question stem.
_________________

Saving was yesterday, heat up the gmatclub.forum's sentiment by spending KUDOS!

PS Please send me PM if I do not respond to your question within 24 hours.

Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 35951
Followers: 6867

Kudos [?]: 90123 [0], given: 10418

Re: If # represents one of the operations +,- and *, is a # [#permalink]

Show Tags

New post 03 Jun 2015, 07:58
Expert's post
1
This post was
BOOKMARKED
reto wrote:
zisis wrote:
If # represents one of the operations +,- and *, is a # (b-c) = (a#b) – (a#c) for all numbers a, b and c.

(1) a#1 is not equal to 1#a for some numbers a

(2) # represents subtraction


Could someone edit this question so it will be an actual question? There is no proper question stem.


What do you mean? Everything is correct there. Similar questions: Operations/functions defining algebraic/arithmetic expressions

Check functions related questions in our Special Questions Directory.

Symbols Representing Arithmetic Operation
Rounding Functions
Various Functions
_________________

New to the Math Forum?
Please read this: All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Verbal Forum Moderator
Verbal Forum Moderator
User avatar
Joined: 29 Apr 2015
Posts: 899
Location: Switzerland
Concentration: Economics, Finance
Schools: LBS MIF '19
WE: Asset Management (Investment Banking)
Followers: 50

Kudos [?]: 1168 [0], given: 302

GMAT ToolKit User Premium Member
Re: If # represents one of the operations +,- and *, is a # [#permalink]

Show Tags

New post 03 Jun 2015, 08:07
Bunuel wrote:
reto wrote:
zisis wrote:
If # represents one of the operations +,- and *, is a # (b-c) = (a#b) – (a#c) for all numbers a, b and c.

(1) a#1 is not equal to 1#a for some numbers a

(2) # represents subtraction


Could someone edit this question so it will be an actual question? There is no proper question stem.


What do you mean? Everything is correct there. Similar questions: Operations/functions defining algebraic/arithmetic expressions

Check functions related questions in our Special Questions Directory.

Symbols Representing Arithmetic Operation
Rounding Functions
Various Functions



The question mark is missing in the question stem.
_________________

Saving was yesterday, heat up the gmatclub.forum's sentiment by spending KUDOS!

PS Please send me PM if I do not respond to your question within 24 hours.

GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 09 Sep 2013
Posts: 12908
Followers: 563

Kudos [?]: 158 [0], given: 0

Premium Member
Re: If # represents one of the operations +,- and *, is a # [#permalink]

Show Tags

New post 28 Sep 2016, 19:59
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 Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Re: If # represents one of the operations +,- and *, is a #   [#permalink] 28 Sep 2016, 19:59
    Similar topics Author Replies Last post
Similar
Topics:
8 Experts publish their posts in the topic If the symbol § represents one of the following operations: mattycen 8 06 Oct 2013, 10:12
If * represents one of the operations +, -, x, is tracyyahoo 3 31 Jul 2011, 03:17
4 Experts publish their posts in the topic If ° represents one of the operations +, –, and ×, siddhans 11 03 Jul 2011, 02:54
Given that the symbol represents one of the operations melguy 5 20 Jun 2011, 23:18
The symbol represents one of the following operations: nsp007 3 30 Jun 2010, 23:52
Display posts from previous: Sort by

If # represents one of the operations +,- and *, is a #

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.