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

 It is currently 18 Dec 2018, 03:00

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

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

Events & Promotions

Events & Promotions in December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
• Happy Christmas 20% Sale! Math Revolution All-In-One Products!

December 20, 2018

December 20, 2018

10:00 PM PST

11:00 PM PST

This is the most inexpensive and attractive price in the market. Get the course now!
• Key Strategies to Master GMAT SC

December 22, 2018

December 22, 2018

07:00 AM PST

09:00 AM PST

Attend this webinar to learn how to leverage Meaning and Logic to solve the most challenging Sentence Correction Questions.

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

Author Message
TAGS:

Hide Tags

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

Show Tags

30 Jun 2012, 07:00
2
14
00:00

Difficulty:

(N/A)

Question Stats:

64% (01:04) correct 36% (00:57) wrong based on 492 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
Math Expert
Joined: 02 Sep 2009
Posts: 51281
Re: If n is an integer, what is the units digit of x?  [#permalink]

Show Tags

30 Jun 2012, 07:07
8
3
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.

_________________
General Discussion
Math Expert
Joined: 02 Sep 2009
Posts: 51281
Re: If n is an integer, what is the units digit of x?  [#permalink]

Show Tags

24 Jun 2013, 02:17
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

_________________
Intern
Joined: 22 May 2013
Posts: 45
Concentration: General Management, Technology
GPA: 3.9
WE: Information Technology (Computer Software)
Re: If n is an integer, what is the units digit of x?  [#permalink]

Show Tags

24 Jun 2013, 08:31
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
_________________

Senior Manager
Joined: 18 Jun 2018
Posts: 254
Re: If n is an integer, what is the units digit of x?  [#permalink]

Show Tags

23 Oct 2018, 08:09
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.
Re: If n is an integer, what is the units digit of x? &nbs [#permalink] 23 Oct 2018, 08:09
Display posts from previous: Sort by