Last visit was: 16 May 2026, 14:55 It is currently 16 May 2026, 14:55
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
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 16 May 2026
Posts: 110,494
Own Kudos:
815,250
 [3]
Given Kudos: 106,270
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 110,494
Kudos: 815,250
 [3]
Kudos
Add Kudos
3
Bookmarks
Bookmark this Post
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 16 May 2026
Posts: 110,494
Own Kudos:
Given Kudos: 106,270
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 110,494
Kudos: 815,250
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
Rebaz
Joined: 14 Feb 2014
Last visit: 11 May 2026
Posts: 145
Own Kudos:
Given Kudos: 4,775
Posts: 145
Kudos: 38
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 16 May 2026
Posts: 110,494
Own Kudos:
815,250
 [1]
Given Kudos: 106,270
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 110,494
Kudos: 815,250
 [1]
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
 
Rebaz
Bunuel

Quote:
How many positive \(n\)-digit integers, where \(n\) is greater than 1, can be formed using nonzero digits such that no two adjacent digits are the same?

A. \(n^8\)
B. \(n^9\)
C. \(8^n\)
D. \(9*8^{(n-1)}\)
E. \(9^n\)

The first digit can take 9 values, from 1 to 9, inclusive.

The next digit can take 8 values, any but the one used for the first digit.

The following digit can also take 8 values, any but the one used for the second digit.

The subsequent digit can also take 8 values, any but the one used for the third digit.

...

And finally, the last, nthnth digit can take 8 values, any but the one used for the second to last digit.

Hence, we have 9 options for the first digit and 8 options for each of the remaining n−1 digits, resulting in a total of 9∗8(n−1)numbers.
Can you please elaborate a little bit more on your solution through an example?


Thanks in advance!
­
In an example where n = 3 (forming a three-digit integer):

First digit: Choose from 1 to 9 (9 options). Suppose we choose 5.
Second digit: Choose any digit except 5 (8 options). Suppose we choose 3.
Third digit: Choose any digit except 3 (8 options). Suppose we choose 7.
The resulting number is 537. This demonstrates the process:

9 options for the first digit.
8 options for each subsequent digit.
This pattern leads to the calculation 9 * 8 * 8 for a three-digit number, following the general formula 9 * 8^(n-1) for any n-digit number.­

Check moe solutions here: 

https://gmatclub.com/forum/how-many-pos ... l#p3339587­
User avatar
enidaddams
Joined: 05 Sep 2025
Last visit: 19 Mar 2026
Posts: 10
Own Kudos:
Given Kudos: 35
Posts: 10
Kudos: 1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
I like the solution - it’s helpful.
Moderators:
Math Expert
110494 posts
Founder
43277 posts