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prolematic problem

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Current Student
Joined: 11 May 2008
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13 Aug 2008, 19:30
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how does one solve problems on such series..?

which of the foll about 1/11+1/12+......+1/20 is true?
>1/2
=1/2
=1/4
=1/8
<1/4.

someone pls give concept as to how to solve such convergent series.. its always a problem for me...

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Director
Joined: 27 May 2008
Posts: 541

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13 Aug 2008, 21:37
arjtryarjtry wrote:
how does one solve problems on such series..?

which of the foll about 1/11+1/12+......+1/20 is true?
>1/2
=1/2
=1/4
=1/8
<1/4.

someone pls give concept as to how to solve such convergent series.. its always a problem for me...

1/11 = 0.091
1/20 = 0.05
all other terms will be between 0.05 and 0.091...

1/15 = 0.067
the sum will be roughly equal to 0.067 * 10 = 0.667 .. (i'm not sure if we can do it in all cases)

0.667 > 0.5 ... option A

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SVP
Joined: 07 Nov 2007
Posts: 1792

Kudos [?]: 1059 [0], given: 5

Location: New York

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14 Aug 2008, 12:38
arjtryarjtry wrote:
how does one solve problems on such series..?

which of the foll about 1/11+1/12+......+1/20 is true?
>1/2
=1/2
=1/4
=1/8
<1/4.

someone pls give concept as to how to solve such convergent series.. its always a problem for me...

1/11+1/12+......+1/20 > 1/20+1/20+......+1/20 = 10/20 =1/2
i.e 1/11+1/12+......+1/20 >1/2

A)

all other options are <1/2
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Re: prolematic problem   [#permalink] 14 Aug 2008, 12:38
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