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# What is the average (arithmetic mean) of a certain series of

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Intern
Joined: 02 Nov 2009
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What is the average (arithmetic mean) of a certain series of [#permalink]

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20 Apr 2010, 08:22
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What is the average (arithmetic mean) of a certain series of N consecutive integers?

(1) The sum of the terms of the series is N.

(2) The sum of the greatest and least terms is 2.

[Reveal] Spoiler:
D

How should I solve this question? Thanks for your help!
Intern
Joined: 14 Jan 2010
Posts: 26
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Kudos [?]: 3 [1] , given: 0

Re: Average/ Mean [#permalink]

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20 Apr 2010, 08:46
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sudai wrote:
What is the average (arithmetic mean) of a certain series of N consecutive integers?

(1) The sum of the terms of the series is N.

(2) The sum of the greatest and least terms is 2.

[Reveal] Spoiler:
D

How should I solve this question? Thanks for your help!

Arith. Mean of any series of consecutive integers = (a+l)/2 where a= first integer, l= last integer.
=> Sum of that series = (number of terms in the series)*(Average of the series) = N*(a+l)/2

Stmt 1) given, Sum= N => N*(a+l)/2= N => Mean = 1 => Sufficient info
Stmt 2) given, a+l= 2 => (a+l)/2 or the Mean = 1 => Sufficient info

Intern
Joined: 02 Nov 2009
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Re: Average/ Mean [#permalink]

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20 Apr 2010, 08:59
PhunsukWangdu wrote:
sudai wrote:
What is the average (arithmetic mean) of a certain series of N consecutive integers?

(1) The sum of the terms of the series is N.

(2) The sum of the greatest and least terms is 2.

[Reveal] Spoiler:
D

How should I solve this question? Thanks for your help!

Arith. Mean of any series of consecutive integers = (a+l)/2 where a= first integer, l= last integer.
=> Sum of that series = (number of terms in the series)*(Average of the series) = N*(a+l)/2

Stmt 1) given, Sum= N => N*(a+l)/2= N => Mean = 1 => Sufficient info
Stmt 2) given, a+l= 2 => (a+l)/2 or the Mean = 1 => Sufficient info

well explained! Thank you!
Re: Average/ Mean   [#permalink] 20 Apr 2010, 08:59
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# What is the average (arithmetic mean) of a certain series of

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