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

 It is currently 06 Jul 2015, 23:41

### 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 June
Open Detailed Calendar

# What is the unit digit??

Author Message
TAGS:
Retired Moderator
Status: The last round
Joined: 18 Jun 2009
Posts: 1317
Concentration: Strategy, General Management
GMAT 1: 680 Q48 V34
Followers: 65

Kudos [?]: 631 [0], given: 157

What is the unit digit?? [#permalink]  31 Oct 2009, 07:26
00:00

Difficulty:

(N/A)

Question Stats:

40% (02:44) correct 60% (01:06) wrong based on 5 sessions
What is the units digit of ( 6^15 - 7^4 - 9^3 )?
A) 8
B) 7
C) 6
D) 5
E) 4
_________________
Retired Moderator
Status: The last round
Joined: 18 Jun 2009
Posts: 1317
Concentration: Strategy, General Management
GMAT 1: 680 Q48 V34
Followers: 65

Kudos [?]: 631 [0], given: 157

Re: What is the unit digit?? [#permalink]  31 Oct 2009, 07:41
I want to tag this post as "number properties" along with "powers". How can I do it??
_________________
Manager
Joined: 13 Oct 2009
Posts: 115
Location: USA
Schools: IU KSB
Followers: 4

Kudos [?]: 60 [0], given: 66

Re: What is the unit digit?? [#permalink]  31 Oct 2009, 07:46
Hussain15 wrote:
What is the units digit of ( 6^15 - 7^4 - 9^3 )?
A) 8
B) 7
C) 6
D) 5
E) 4

Is OA "E" ?

Unit digit for term 6^15 = 6
Unit digit for term 7^4 = 1
Unit digit for term 9^3 = 9

altogether unit digit for ( 6^15 - 7^4 - 9^3 ) = 6 -1 -9 = 4

Thanks.

Last edited by swatirpr on 31 Oct 2009, 08:02, edited 1 time in total.
Retired Moderator
Status: The last round
Joined: 18 Jun 2009
Posts: 1317
Concentration: Strategy, General Management
GMAT 1: 680 Q48 V34
Followers: 65

Kudos [?]: 631 [0], given: 157

Re: What is the unit digit?? [#permalink]  31 Oct 2009, 07:51

OA and OE will be posted later.
_________________
Senior Manager
Joined: 18 Aug 2009
Posts: 304
Followers: 3

Kudos [?]: 129 [1] , given: 9

Re: What is the unit digit?? [#permalink]  31 Oct 2009, 09:22
1
KUDOS
swatirpr wrote:
Hussain15 wrote:
What is the units digit of ( 6^15 - 7^4 - 9^3 )?
A) 8
B) 7
C) 6
D) 5
E) 4

Is OA "E" ?

Unit digit for term 6^15 = 6
Unit digit for term 7^4 = 1
Unit digit for term 9^3 = 9

altogether unit digit for ( 6^15 - 7^4 - 9^3 ) = 6 -1 -9 = 4

Thanks.

I agree with your approach. But IMO ans is 6.(C)
just this last step... 6-1-9=6

take for example
436 (6^15 is bigger than other 2)
-71
-89
units digit=6-0=6
Retired Moderator
Status: The last round
Joined: 18 Jun 2009
Posts: 1317
Concentration: Strategy, General Management
GMAT 1: 680 Q48 V34
Followers: 65

Kudos [?]: 631 [0], given: 157

Re: What is the unit digit?? [#permalink]  31 Oct 2009, 23:25
Thanks for the input.

OA is "C".
_________________
Re: What is the unit digit??   [#permalink] 31 Oct 2009, 23:25
Similar topics Replies Last post
Similar
Topics:
3 What is the units digit of 2222^(333)*3333^(222)? 7 28 Jan 2012, 10:55
4 What is the units digit of 18^47 ? 11 21 Oct 2010, 16:40
6 What is the unit's digit of 7^75 + 6 ? 8 14 Sep 2010, 11:58
If x is a positive integer, what is the units digit of 1 19 Jul 2006, 02:08
Display posts from previous: Sort by