Last visit was: 18 Nov 2025, 15:48 It is currently 18 Nov 2025, 15:48
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: 18 Nov 2025
Posts: 105,355
Own Kudos:
778,068
 [9]
Given Kudos: 99,964
Products:
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 105,355
Kudos: 778,068
 [9]
Kudos
Add Kudos
9
Bookmarks
Bookmark this Post
Most Helpful Reply
User avatar
IanStewart
User avatar
GMAT Tutor
Joined: 24 Jun 2008
Last visit: 16 Nov 2025
Posts: 4,145
Own Kudos:
10,983
 [11]
Given Kudos: 99
Expert
Expert reply
Posts: 4,145
Kudos: 10,983
 [11]
10
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
General Discussion
User avatar
rajatchopra1994
Joined: 16 Feb 2015
Last visit: 22 Jun 2024
Posts: 1,056
Own Kudos:
1,252
 [1]
Given Kudos: 30
Location: United States
Posts: 1,056
Kudos: 1,252
 [1]
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
avatar
Pratikb009
Joined: 17 Mar 2021
Last visit: 10 Nov 2022
Posts: 3
Own Kudos:
4
 [3]
Given Kudos: 34
Posts: 3
Kudos: 4
 [3]
2
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Given n=18
a=?
AP = n,n+1.....n+17
Sum of all the numbers of AP (Sn) =n/2(2a+[n-1]d)
Since WKT,

Average = Sum of all numbers/ total numbers

22.5 =n/2 * (2a+{n-1}d)/18
22.5 =18/2 * (2a+{18-1}1)/18
(22.5*18)/9 = 2a+17
45=2a+17
45-17 = 28 = 2a
a=14
avatar
PranavMahadik
Joined: 12 Apr 2021
Last visit: 21 Nov 2021
Posts: 8
Own Kudos:
Given Kudos: 14
Posts: 8
Kudos: 3
Kudos
Add Kudos
Bookmarks
Bookmark this Post
18{[x + (x+17)]/2} = (18*22.5)
18{[x + (x+17)]/2} = 405
9[x + (x+17)] = 405
9x + 9x + 153 = 405
18x = 252
x = 14

The answer IMO: D
User avatar
rito54
Joined: 28 Jun 2024
Last visit: 28 Oct 2024
Posts: 33
Own Kudos:
Given Kudos: 25
Posts: 33
Kudos: 6
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Hello, could someone clarify why the largest term is n+17 and not n+18 please? Thank you!
Moderators:
Math Expert
105355 posts
Tuck School Moderator
805 posts