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If N = 1/3 +1/3^2 +1/3^3, then N is between A. 0 and 1/9 B.

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Current Student
Joined: 11 May 2008
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If N = 1/3 +1/3^2 +1/3^3, then N is between A. 0 and 1/9 B. [#permalink]

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25 Jul 2008, 03:43
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

If N = 1/3 +1/3^2 +1/3^3, then N is between
A. 0 and 1/9
B. 1/9 and 1/3
C. 1/3 and 8/9
D. 8/9 and 4/3

Kudos [?]: 222 [0], given: 0

Current Student
Joined: 12 Jun 2008
Posts: 287

Kudos [?]: 58 [0], given: 0

Schools: INSEAD Class of July '10

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25 Jul 2008, 04:13
N = 1/3 + something positive ==> N > 1/3

N = 3/9 + 1/9 + 1/9*1/3 < 3/9 + 1/9 + 1/9 = 5/9 ==> N < 5/9

Therefore: 1/3 < N < 5/9 < 8/9

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Manager
Joined: 27 May 2008
Posts: 140

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25 Jul 2008, 07:46

Solving the equation the value is 13/27
Which is closer to 0.5

Only option C suits.

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Manager
Joined: 14 Jun 2008
Posts: 162

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25 Jul 2008, 07:51
arjtryarjtry wrote:
If N = 1/3 +1/3^2 +1/3^3, then N is between
A. 0 and 1/9
B. 1/9 and 1/3
C. 1/3 and 8/9
D. 8/9 and 4/3

summing the equation, we get a total of 10 / 27

to compare, i converted everything to a denominator of 27

A) 0 and 3/27 - nope
B) 3/27 and 9 / 27 - nope
C) 9/27 and 24/27 - yes!!!

Kudos [?]: 37 [0], given: 0

Re: SERIES...   [#permalink] 25 Jul 2008, 07:51
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