GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 13 Nov 2019, 07:43

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

Confirm Cancel

If n is an integer, what is the units digit of x?

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

Hide Tags

Find Similar Topics 
Intern
Intern
avatar
Joined: 30 Jun 2012
Posts: 7
If n is an integer, what is the units digit of x?  [#permalink]

Show Tags

New post 30 Jun 2012, 08:00
2
16
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

64% (01:29) correct 36% (01:19) wrong based on 576 sessions

HideShow timer Statistics

If n is an integer, what is the units digit of x?

(1) x = (25^2)/(10^n)

(2) n^2 = 1
Most Helpful Expert Reply
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 59017
Re: If n is an integer, what is the units digit of x?  [#permalink]

Show Tags

New post 30 Jun 2012, 08:07
8
4
If n is an integer, what is the units digit of x?

(1) x = (25^2)/(10^n). If \(n=0\) then \(x=\frac{25^2}{10^0}=625\) and the units digit of \(x\) is 5 but if \(n=-1\) then \(x=\frac{25^2}{10^{-1}}=6250\) and the units digit of \(x\) is 0. Not sufficient.

(2) n^2 = 1 --> \(n=1\) or \(n=-1\). Not sufficient as no info about \(x\).

(1)+(2) If \(n=1\) then \(x=\frac{25^2}{10^1}=62.5\) and the units digit of \(x\) is 2 but if \(n=-1\) then \(x=\frac{25^2}{10^{-1}}=6250\) and the units digit of \(x\) is 0. Not sufficient.

Answer: E.
_________________
General Discussion
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 59017
Re: If n is an integer, what is the units digit of x?  [#permalink]

Show Tags

New post 24 Jun 2013, 03:17
Intern
Intern
avatar
Joined: 22 May 2013
Posts: 43
Concentration: General Management, Technology
GPA: 3.9
WE: Information Technology (Computer Software)
GMAT ToolKit User
Re: If n is an integer, what is the units digit of x?  [#permalink]

Show Tags

New post 24 Jun 2013, 09:31
1
Bunuel wrote:
Bumping for review and further discussion*. Get a kudos point for an alternative solution!

*New project from GMAT Club!!! Check HERE

All DS Fractions/Ratios/Decimals questions: search.php?search_id=tag&tag_id=36
All PS Fractions/Ratios/Decimals questions: search.php?search_id=tag&tag_id=57


Question: Its a value question, we need to know the units place of x, so irrespective of the no if we can get the same units place always, this should be fine.

(1) x = (25^2)/(10^n)

n is an integer, can be positive/negative and even/odd anything.
With any little slight change in value of n the units place digit will change => Not sufficient

(2) n^2 =1

Well n's units place must be always 1, but what about the relation b/w n and x? we still dont know anything about x => Not sufficient

Both combined. (1) + (2)

take n= -1 and n=1
again without any calculation we can see that we will get x=6250 and 62.5 respectively => Not sufficient

Ans=>E
_________________
PS: Like my approach? Please Help me with some Kudos. :-)
Senior Manager
Senior Manager
User avatar
D
Joined: 18 Jun 2018
Posts: 257
Re: If n is an integer, what is the units digit of x?  [#permalink]

Show Tags

New post 23 Oct 2018, 09:09
ferrarih wrote:
If n is an integer, what is the units digit of x?

(1) x = (25^2)/(10^n)

(2) n^2 = 1


OA: E

\((1)\quad x = \frac{25^2}{10^n}\)

taking value of \(n=0\), we get \(x=\frac{25^2}{10^0}\) ; \(x =625\)
Units digit is \(5\).

taking value of \(n=1\), we get \(x=\frac{25^2}{10^1}\) ; \(x =62.5\)
Units digit is \(2\).

As we are not getting a unique value of units digit of \(x\), Statement \(1\) alone is insufficient.

\((2)\quad n^2 = 1\)
\(n^2-1=0\); \(n\) can be \(1\) or \(-1\).
Statement \(2\) does not give any information about \(x\) , Statement \(2\) alone is insufficient.

Combining \((1)\) and \((2)\), we get
Putting \(n=1\), We get \(x=\frac{25^2}{10^1}\) ; \(x =62.5\)
Units digit is \(2\).

Putting \(n=-1\), We get \(x=\frac{25^2}{10^{-1}}\) ; \(x =6250\)
Units digit is \(0\).

As we are not getting a unique value of units digit of \(x\), Combining Statement \(1\) and Statement \(2\) also is not sufficient.
GMAT Club Bot
Re: If n is an integer, what is the units digit of x?   [#permalink] 23 Oct 2018, 09:09
Display posts from previous: Sort by

If n is an integer, what is the units digit of x?

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





Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne