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What is the average of eleven consecutive integers? 1) [#permalink]
 26 Mar 2006, 22:44
What is the average of eleven consecutive integers?
1) average of first 9 integers is 7
2) average of last 9 integers is 9
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Director
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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
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SVP
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"D" it is 
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Re: Average this :) [#permalink]
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. 
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VP
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Fellow GMATers,
What if it is a decreasing sequence....
N, N-1 , N-2.....
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lhotseface wrote: Fellow GMATers,
What if it is a decreasing sequence....
N, N-1 , N-2.....
I think still we can determine!
The numbers are arranged in reverse order, so it can still be determined. Am I right?
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VP
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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,x-1,x-2.....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, N-1 , N-2..... I think still we can determine! The numbers are arranged in reverse order, so it can still be determined. Am I right? |
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Director
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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
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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 
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VP
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if u represent the set of nos as
n, n+1... n+10 its qte easy..
ans is D
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Director
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lhotseface wrote: Fellow GMATers,
What if it is a decreasing sequence....
N, N-1 , N-2.....
As I know in such type of Q GMAT always use increasing order.
Am I right? 
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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
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Consecutive integers are integers n1 and n2, such that n2-n1=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.
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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 .
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close
