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

It is currently 03 May 2016, 02:18
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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

What is the last digit of

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Intern
Intern
avatar
Joined: 25 Oct 2009
Posts: 24
Schools: Wharton, HBS, Stanford
Followers: 0

Kudos [?]: 34 [0], given: 12

What is the last digit of [#permalink]

Show Tags

New post 11 Jan 2010, 14:50
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 100% (00:33) wrong based on 5 sessions

HideShow timer Statictics

What is the last digit of \(9^1+99^2+999^3+...+(10^n-1)^n\)?

(1) n is even
(2) n is prime

OA is
[Reveal] Spoiler:
A


OE:
[Reveal] Spoiler:
We have the sum of integers:

\((..9) + (..1) + (..9) + (..1) + ...\)

Statement (1) by itself is sufficient. If n is even then this sum ends with 0. If it's odd, then this sum ends with 9.

Statement (2) by itself is insufficient. (2 is prime and even, 3 is prime and odd)


Question:
[Reveal] Spoiler:
it seems from question's stem that n>3, which combined with Statement (2) means that n is odd. As a result, the sum always ends with 9. If this correct, the answer should be D.

Please, give you opinion.
_________________

KUDOS if you find it helpful ;)

1 KUDOS received
Current Student
User avatar
Joined: 05 Aug 2008
Posts: 1262
Schools: Ross 2012
WE 1: 5 Years at Fortune 50 Company in Manufacturing
Followers: 21

Kudos [?]: 169 [1] , given: 20

Re: What is the last digit of ...? (GMATClub test m10, q36) [#permalink]

Show Tags

New post 11 Jan 2010, 17:18
1
This post received
KUDOS
You make an interesting point. I think the idea is that N doesn't have to be greater than 3. Although the question has n being at least 3. I think in it's written form, with the ..., N can be one, two, or three. Which is why it is not sufficient.

Also for Data Sufficiency. The two statements cannont be contridictory. So if you were to use like a) and line b) both statements would be contridictory with since the number cannot be prime and even and greater than 3. so your assumption of n>3 is wrong.
_________________

GMAT Club Premium Membership - big benefits and savings

GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 09 Sep 2013
Posts: 9264
Followers: 455

Kudos [?]: 115 [0], given: 0

Premium Member
Re: What is the last digit of [#permalink]

Show Tags

New post 11 Mar 2016, 21:54
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: What is the last digit of   [#permalink] 11 Mar 2016, 21:54
Display posts from previous: Sort by

What is the last digit of

  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®.