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.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

A list of 18 numbers is arranged from the least to the [#permalink]

Show Tags

01 Oct 2003, 22:36

00:00

A

B

C

D

E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct
0% (00:00) wrong based on 0 sessions

HideShow timer Statistics

This topic is locked. If you want to discuss this question please re-post it in the respective forum.

2. A list of 18 numbers is arranged from the least to
the greatest. The average of the first n numbers in the list is x
and the average of the remaining numbers is y. If the average of x
and y is equal to the average of all 18 numbers, which of the following
msut be true:

A) n = 1
B) n = 9
C) n = 17
D) 1 < n < 9
E) 9 < n < 17

i admit that i'm having a hard time wrapping my brain around this.

Of course, if they are 18 consecutive numbers, then the average of all would be the one in the middle, and the average of the first 9 would be the middle of the first 9, and the average of the second 9 would be the middle of the second 9, and the average of those two would be the middle of everything, since consecutives just always work out so nicely like that.

My problem to understand is what if they aren't consecutive. Would this still be possible?

But it doesn't matter, because I've just shown that it is true that this could come up 9, and there's only one answer in the whole list that includes 9, and that's B. D and E both exclude 9.

So I'm going with B, having not tried the non-consecutive option.