NEW HERE? LEARN MORE
closeclose
Last visit was: 24 Apr 2024, 10:33 It is currently 24 Apr 2024, 10:33
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

What is the units digit of Y?

SORT BY:
Date
Kudos
Tags:
Poor Qualityx      
Find Similar Topics 
Show Tags
Hide Tags
User avatar
sudhir18n
Current Student
Joined: 26 May 2005
Posts: 356
Own Kudos [?]: 566 [4]
Given Kudos: 13
Send PM
What is the units digit of Y? [#permalink] New post   29 Jun 2011, 01:25
1
Kudos
3
Bookmarks
00:00
A
B
C
D
E

Difficulty:

25% (medium)

Question Stats:

69% (01:08) correct 31% (01:10) wrong based on 159 sessions
Hide Show timer Statistics
What is the units digit of Y?

(1) The units digit of Y^2 is equal to 6.
(2) The units digit of (Y+1)^2 is equal to 5


Its fairly simple problem , but I have a problem with the OA.
St1: can be 4 or 6 or - 4 or -6 ... hence in sufficient
st2: can be 4 or -6... .. The question doesnt mention the Y is a postive integer..

This Question is Locked Due to Poor Quality
Hi there,
The question you've reached has been archived due to not meeting our community quality standards. No more replies are possible here.
Looking for better-quality questions? Check out the 'Similar Questions' block below for a list of similar but high-quality questions.
Want to join other relevant Problem Solving discussions? Visit our Data Sufficiency (DS) Forum for the most recent and top-quality discussions.
Thank you for understanding, and happy exploring!
ShowHide Answer
Official Answer
B
User avatar
fluke
Retired Moderator
Joined: 20 Dec 2010
Posts: 1114
Own Kudos [?]: 4702 [0]
Given Kudos: 376
Send PM
Re: What is the units digit of Y? [#permalink] New post   29 Jun 2011, 03:56
sudhir18n wrote:
Q: What is the units digit of Y?
st:1 The units digit of Y^2 is equal to 6.
St:2 The units digit of (Y+1)^2 is equal to 5


Its fairly simple problem , but I have a problem with the OA.
St1: can be 4 or 6 or - 4 or -6 ... hence in sufficient
st2: can be 4 or -6... .. The question doesnt mention the Y is a postive integer..


Good catch!!! Stem should have mentioned "positive integer Y", OR the OA should be "E". Please notify them.
User avatar
fivedaysleft
Manager
Manager
Joined: 29 Jun 2011
Posts: 50
Own Kudos [?]: 27 [0]
Given Kudos: 46
 Q48  V34
Send PM
Re: What is the units digit of Y? [#permalink] New post   Updated on: 02 Jul 2011, 11:57
no need to mention positive integer...the question says find "units digit". by definition, units digits can only be non negative integers. so there is no ambiguity.

Originally posted by fivedaysleft on 30 Jun 2011, 01:24.
Last edited by fivedaysleft on 02 Jul 2011, 11:57, edited 1 time in total.
User avatar
sudhir18n
Current Student
Joined: 26 May 2005
Posts: 356
Own Kudos [?]: 566 [0]
Given Kudos: 13
Send PM
Re: What is the units digit of Y? [#permalink] New post   30 Jun 2011, 02:58
[quote="fivedaysleft"]no need to mention positive integer...the question says find "units digit". by definition, units digits can only be positve integers. so there is no ambiguity.

quote]

Can anyone confirm this? I'm not aware of any such rule.
User avatar
Chetangupta
Manager
Manager
Joined: 23 Jan 2011
Posts: 84
Own Kudos [?]: 418 [0]
Given Kudos: 13
Send PM
Re: What is the units digit of Y? [#permalink] New post   30 Jun 2011, 03:15
I think b is the correct answer. At first even I went for E but a second read of the question says unit digit of Y- so has to be positive. Else the question could be what is Y?

So solution could be as follows:
1) Could be 4 or 6- A and D are out
2) has to be 4- sufficient, B is the answer.

B
User avatar
fluke
Retired Moderator
Joined: 20 Dec 2010
Posts: 1114
Own Kudos [?]: 4702 [0]
Given Kudos: 376
Send PM
Re: What is the units digit of Y? [#permalink] New post   30 Jun 2011, 03:18
sudhir18n wrote:
fivedaysleft wrote:
no need to mention positive integer...the question says find "units digit". by definition, units digits can only be positve integers. so there is no ambiguity.


Can anyone confirm this? I'm not aware of any such rule.


fivedaysleft mentioned a partially correct rule. Digit=0,1,2,3,4,5,6,7,8,9 (So a digit is non-negative one-digit integer)

But, note that y is an Integer, any Integer, NOT necessarily a digit.

Unit's digit of "y" is a digit.

y can be -525324324342424246; Here unit's digit of y=6
OR
y can be +434252424242424244; Here unit's digit of y=4

Please send a mail to MGMAT and get it clarified.
User avatar
fivedaysleft
Manager
Manager
Joined: 29 Jun 2011
Posts: 50
Own Kudos [?]: 27 [0]
Given Kudos: 46
 Q48  V34
Send PM
Re: What is the units digit of Y? [#permalink] New post   02 Jul 2011, 12:00
fluke wrote:
y can be -525324324342424246; Here unit's digit of y=6
OR
y can be +434252424242424244; Here unit's digit of y=4

Please send a mail to MGMAT and get it clarified.


i dont think the ambiguity is too great.
because if a problem is given on the number -525324324342424246
it can always be assigned as (-1)*(525324324342424246) and we can proceed. There might be a difference in definitions of digits and integers at the fundamental level but is it necessary for GMAT? i do not believe so.
correct me if i am wrong. :?
User avatar
fluke
Retired Moderator
Joined: 20 Dec 2010
Posts: 1114
Own Kudos [?]: 4702 [0]
Given Kudos: 376
Send PM
Re: What is the units digit of Y? [#permalink] New post   02 Jul 2011, 12:25
fivedaysleft wrote:
fluke wrote:
y can be -525324324342424246; Here unit's digit of y=6
OR
y can be +434252424242424244; Here unit's digit of y=4

Please send a mail to MGMAT and get it clarified.


i dont think the ambiguity is too great.
because if a problem is given on the number -525324324342424246
it can always be assigned as (-1)*(525324324342424246) and we can proceed. There might be a difference in definitions of digits and integers at the fundamental level but is it necessary for GMAT? i do not believe so.
correct me if i am wrong. :?


If we can find one such ambiguity in OG's OR GmatPrep, then we can think about taking it for granted. It is highly unlikely that GMAT will ever frustrate you with such dilemma. Skip this question and let's wait for MGMAT's response.
User avatar
L
IanStewart
GMAT Tutor
Joined: 24 Jun 2008
Posts: 4128
Own Kudos [?]: 9241 [1]
Given Kudos: 91
 Q51  V47
Send PM
Re: What is the units digit of Y? [#permalink] New post   03 Jul 2011, 04:53
1
Kudos
Expert Reply
On the real GMAT, any question about units digits will be restricted to *positive* numbers only. So if this were an actual GMAT question, the stem would tell you that Y is positive. I agree that this question is ambiguous as written and needs to be corrected, but if you understand how you'd solve the question if it read "If Y is a positive integer, what it the units digit of Y?" then you've taken away everything you need to take away from the problem.
User avatar
B
tann412
Intern
Intern
Joined: 09 Apr 2018
Posts: 16
Own Kudos [?]: 18 [0]
Given Kudos: 35
Send PM
Re: What is the units digit of Y? [#permalink] New post   14 Oct 2018, 07:32
Hi Bunuel, requesting a clarification on this one.

Why can't we take the case of NEGATIVE Numbers in this one?
Do we always assume that for any question involving a DIGIT on the GMAT, the number is a positive number?
Either the Question is drafted incorrectly or the OA is incorrect.

Here, using B, one has a definitive ans as 4 if its a positive number.

What if its (-8372893729836 + 1)^2. The units digit is still 5.
So if we consider both positive and negative numbers, we have 821829714 or -434236, y has units digit 4 or 6.

Questions should set a condition: Positive or Negative Integer y.

This Question is Locked Due to Poor Quality
Hi there,
The question you've reached has been archived due to not meeting our community quality standards. No more replies are possible here.
Looking for better-quality questions? Check out the 'Similar Questions' block below for a list of similar but high-quality questions.
Want to join other relevant Problem Solving discussions? Visit our Data Sufficiency (DS) Forum for the most recent and top-quality discussions.
Thank you for understanding, and happy exploring!
GMAT Club Bot
gmatclubot
Re: What is the units digit of Y? [#permalink]
14 Oct 2018, 07:32
Moderator:
Bunuel
Math Expert
92902 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