Author 
Message 
VP
Joined: 20 Sep 2005
Posts: 1017

What is the average of eleven consecutive integers? 1) [#permalink]
Show Tags
26 Mar 2006, 22:44
This topic is locked. If you want to discuss this question please repost it in the respective forum.
What is the average of eleven consecutive integers?
1) average of first 9 integers is 7
2) average of last 9 integers is 9



Director
Joined: 13 Nov 2003
Posts: 789
Location: BULGARIA

Hallo face,
Consecutive integers are:
N, N+1, N+2, N+10 then
from A) 9N+36=63 N=3
from B) 9N+54=81 N=3
so D) seems correct IMO
Regards



SVP
Joined: 14 Dec 2004
Posts: 1689

"D" it is



SVP
Joined: 05 Apr 2005
Posts: 1710

Re: Average this :) [#permalink]
Show Tags
27 Mar 2006, 14:08
lhotseface wrote: What is the average of eleven consecutive integers? 1) average of first 9 integers is 7 2) average of last 9 integers is 9
D too.



VP
Joined: 20 Sep 2005
Posts: 1017

Fellow GMATers,
What if it is a decreasing sequence....
N, N1 , N2.....



SVP
Joined: 14 Dec 2004
Posts: 1689

lhotseface wrote: Fellow GMATers,
What if it is a decreasing sequence.... N, N1 , N2.....
I think still we can determine!
The numbers are arranged in reverse order, so it can still be determined. Am I right?



VP
Joined: 20 Sep 2005
Posts: 1017

Here is where I differ...kindly point out the flaw..I can't spot one
If the numbers are x, x+1, x+2.....then statement I gives us....
(9x + 36)/9 = 7 => x = 3
and the average of 11 numbers is ( 11(3) + 55 )/11 = 8.
If the numbers are x,x1,x2.....then statement I gives us....
(9x  36)/9 = 7 => x = 11
and the average of 11 numbers is ( 11(11)  55 )/11 = 6.
Thus, we get two different values and hence A is INSUFF IMHO and similarly B is INSUFF.
vivek123 wrote: lhotseface wrote: Fellow GMATers,
What if it is a decreasing sequence.... N, N1 , N2..... I think still we can determine! The numbers are arranged in reverse order, so it can still be determined. Am I right?



Director
Joined: 13 Nov 2003
Posts: 789
Location: BULGARIA

Your reasoning is flawless IMO
possible sets
3,4,5,6,7,8,9,10,11,12,13
11,10,9,8,7,6,5,4,3,2,1
The average for first 9 terms for both is 7 so A) is insufficient and as you mentioned B) is also insufficient by the same reasoning.
Then from both statements togehter seems that only one set of numbers can be determined.
Good reasoning Ihotseface



SVP
Joined: 14 Dec 2004
Posts: 1689

lhotseface wrote: Here is where I differ...kindly point out the flaw..I can't spot one
Actually, I meant the same, that the value can still be determined, thus D can't be the answer. Sorry for putting it in wrong way



VP
Joined: 29 Apr 2003
Posts: 1403

if u represent the set of nos as
n, n+1... n+10 its qte easy..
ans is D



Senior Manager
Joined: 08 Jun 2004
Posts: 495
Location: Europe

lhotseface wrote: Fellow GMATers,
What if it is a decreasing sequence.... N, N1 , N2.....
As I know in such type of Q GMAT always use increasing order.
Am I right?



Manager
Joined: 04 Jan 2006
Posts: 58

Can anybody explain this line pls?
(9x + 36)/9 = 7 => x = 3
My expln: (Assuming increasing order)
stmt 1: Since the nos are consecutive 7 is the 5th element. For 11 numbers, the average should be the 6th number. That is 8.
Stmt2:
Same logic as above



Intern
Joined: 03 Mar 2006
Posts: 19

Consecutive integers are integers n1 and n2, such that n2n1=1 , i.e., n2 follows immediately after n1.
If the Sequence is in decreasing order.. then n2  n1 = 1... so by definition they are not consecutive.
If I'm wrong, somebody please let me know.



Manager
Joined: 13 Dec 2005
Posts: 224
Location: Milwaukee,WI

I concurr with RAO ... the defination of CONSECUTIVE INTEGER is the integers that follows in sequence,each number being one greater than the previous number ,represented by n,n+1,n+2 .....where n is any number ...
Hence the answer for the question is D .










