Find all School-related info fast with the new School-Specific MBA Forum

It is currently 18 Sep 2014, 00:02

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

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

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Manager
Manager
avatar
Joined: 16 Feb 2010
Posts: 225
Followers: 2

Kudos [?]: 68 [0], given: 16

GMAT Tests User
If # represents one of the operations +,- and *, is a # [#permalink] New post 19 Sep 2010, 14:49
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

73% (01:31) correct 27% (01:08) wrong based on 60 sessions
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.
Senior Manager
Senior Manager
avatar
Joined: 20 Jul 2010
Posts: 271
Followers: 2

Kudos [?]: 39 [0], given: 9

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

Manager
Manager
avatar
Joined: 23 Sep 2009
Posts: 154
Followers: 1

Kudos [?]: 15 [0], given: 37

Re: If # represents one of the operations +,- and *, is a # [#permalink] New post 19 Sep 2010, 15:50
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

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

Kudos [?]: 2 [0], given: 0

Re: If # represents one of the operations +,- and *, is a # [#permalink] 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: 29671
Followers: 3495

Kudos [?]: 26309 [0], given: 2709

Re: If # represents one of the operations +,- and *, is a # [#permalink] New post 19 Sep 2010, 23:14
Expert's post
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 MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

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

Kudos [?]: 2 [0], given: 0

Re: If # represents one of the operations +,- and *, is a # [#permalink] 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 [?]: 23 [0], given: 15

GMAT Tests User
Re: If # represents one of the operations +,- and *, is a # [#permalink] 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: 2

Kudos [?]: 80 [0], given: 5

Re: If # represents one of the operations +,- and *, is a # [#permalink] 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)
Re: If # represents one of the operations +,- and *, is a #   [#permalink] 21 Sep 2010, 09:55
    Similar topics Author Replies Last post
Similar
Topics:
If # represents one of the operations +, -, and *, is k # puma 4 24 Mar 2008, 12:03
If represents one of the operations +, , and , is amansingla4 2 15 May 2006, 01:35
If # represents one of the operations +, -, and x, is foolbox 2 11 Apr 2006, 05:52
If & represents one of the operations +, -, and *, is vikramm 7 21 Sep 2005, 17:07
If # represents one of the following operations +,-, and *, singh 3 20 Feb 2005, 08:33
Display posts from previous: Sort by

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

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| 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®.