Last visit was: 03 May 2026, 00:06 It is currently 03 May 2026, 00:06
Home
Messages
Tests
Schools
Events
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
User avatar
peachtree
User avatar
Joined: 10 Jun 2006
Last visit: 19 Jul 2006
Posts: 7
Posts: 7
Kudos: 0
From a Kaplan Practice Test: What is the units digit of 03 Jul 2006, 08:33
Kudos
Add Kudos
Bookmarks
Bookmark this Post
From a Kaplan Practice Test:

What is the units digit of (9)^5 * (10)^3 *(7)^3?

Their explanation skips several steps. Could someone please explain the quickest way to solve this problem?



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block below for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!
User avatar
acfuture
User avatar
Joined: 19 Apr 2006
Last visit: 23 Jun 2007
Posts: 118
Own Kudos:
9
Posts: 118
Kudos: 9
From a Kaplan Practice Test: What is the units digit of 03 Jul 2006, 08:45
Kudos
Add Kudos
Bookmarks
Bookmark this Post
peachtree
From a Kaplan Practice Test:

What is the units digit of (9)^5 * (10)^3 *(7)^3?

Their explanation skips several steps. Could someone please explain the quickest way to solve this problem?
Show more


9^2 = 81
9^3 = 729
9^4 = 6561
9^5 = 59049
You see the pattern where 1 and 9 switches back and forth for the unit number.

10^3 = 1000 with a unit number of 0
7^3 = 343 with a unit number of 3.

But when we are multiplying all three, it should jump out you that you are going to multiply by 9*0*3. Therefore the unit number is 0.
User avatar
peachtree
User avatar
Joined: 10 Jun 2006
Last visit: 19 Jul 2006
Posts: 7
Posts: 7
Kudos: 0
From a Kaplan Practice Test: What is the units digit of 03 Jul 2006, 09:20
Kudos
Add Kudos
Bookmarks
Bookmark this Post
if the question was 9^5 * 13^3 * 7^3?

(sorry I typed it incorrectly the first time.)

i get what you're saying though: to look for a pattern.

in the kaplan answer, they said to think of (13)^3*(7)^3 as (13*7)^7.
Does that make sense to you?
User avatar
acfuture
User avatar
Joined: 19 Apr 2006
Last visit: 23 Jun 2007
Posts: 118
Own Kudos:
9
Posts: 118
Kudos: 9
From a Kaplan Practice Test: What is the units digit of 03 Jul 2006, 09:43
Kudos
Add Kudos
Bookmarks
Bookmark this Post
peachtree
if the question was 9^5 * 13^3 * 7^3?

(sorry I typed it incorrectly the first time.)

i get what you're saying though: to look for a pattern.

in the kaplan answer, they said to think of (13)^3*(7)^3 as (13*7)^7.
Does that make sense to you?
Show more


I am kind of confused...
(13)^3*(7)^3 = 753571
(13*7)^3 = (91)^3 = 753571
(13*7)^7 = (i cheated and used the calculator) = 51676101935731

only the unit number matches. By any change is the (13*7)^7 a typo and needs to be (13*7)^3? if it is a typo, I get it, if not... I am not sure...but one of the Math guru will post a response... :-D
User avatar
peachtree
User avatar
Joined: 10 Jun 2006
Last visit: 19 Jul 2006
Posts: 7
Posts: 7
Kudos: 0
From a Kaplan Practice Test: What is the units digit of 03 Jul 2006, 11:19
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I thought it must have been a typo too. Thanks for your help!
User avatar
ps_dahiya
User avatar
Joined: 20 Nov 2005
Last visit: 15 Oct 2019
Posts: 1,486
Own Kudos:
1,239
Concentration: Strategy, Entrepreneurship
Schools:Completed at SAID BUSINESS SCHOOL, OXFORD - Class of 2008
Posts: 1,486
Kudos: 1,239
From a Kaplan Practice Test: What is the units digit of 03 Jul 2006, 16:36
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Quickest way would be find unit digit of each term by taking only the unit digit:

Unit digit of 9^5 = 9
Unit digit of 13^5 (Consider only 3 instead of 13) = 7
Unit digit of 7^3 = 3

Now unit digit of multiplication of 9, 7 and 3 = 9
User avatar
necromonger
User avatar
Joined: 07 Jun 2006
Last visit: 06 Mar 2010
Posts: 458
Own Kudos:
222
Posts: 458
Kudos: 222
From a Kaplan Practice Test: What is the units digit of 03 Jul 2006, 18:12
Kudos
Add Kudos
Bookmarks
Bookmark this Post
peachtree
From a Kaplan Practice Test:

What is the units digit of (9)^5 * (13)^3 *(7)^3?

Their explanation skips several steps. Could someone please explain the quickest way to solve this problem?
Show more


9^5 = 3^(2*5) = 3^10 ..pattern is 9,7,1,3,9,7,1,7,9.. so ends with 9

13^3 -> ends with 7, (3*3*3)

and 7^3 ends with 9*7->3

so the final number would end with 3*9*1 ->7



Archived Topic
Hi there,
This topic has been closed and archived due to inactivity or violation of community quality standards. No more replies are possible here.
Where to now? Join ongoing discussions on thousands of quality questions in our Quantitative Questions Forum
Still interested in this question? Check out the "Best Topics" block above for a better discussion on this exact question, as well as several more related questions.
Thank you for understanding, and happy exploring!