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What is the range ans sum of of Sn Sn=

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SVP
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What is the range ans sum of of Sn Sn= [#permalink] New post 13 Oct 2006, 12:58
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

What is the range ans sum of of Sn
Sn= 1/34+1/35+1/36+1/37......+1/66
Director
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 [#permalink] New post 13 Oct 2006, 18:28
Range: 1/34 - 1/66 = 8/187

Sum: 33/2(1/33 + 1/66) = 25/34

The highlighted part should be 34. Explanation two posts below.

(edited to correct typo)

Last edited by anandsebastin on 13 Oct 2006, 19:43, edited 1 time in total.
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 [#permalink] New post 13 Oct 2006, 19:31
Code:
Sum: 33/2(1/33 + 1/66) = 25/34


Anand, pls explain.
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 [#permalink] New post 13 Oct 2006, 19:40
girikorat wrote:
Sum: 33/2(1/33 + 1/66) = 25/34

Anand, pls explain.


Sorry Giri!

Sum of a series = n/2(a+l)
where, n = number of terms
a = first term
l = last term

Here, 1/33 to 1/66. So n=66-34 +1 (since 34 is also included)

I made a typo (highlighted) in the original post. It should be

33/2(1/34+1/66)

Hope that is right and is of help!
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 [#permalink] New post 13 Oct 2006, 21:22
Folks, u r doing a mistake here.

Sum of the series will be n/2 (a+l) provided the given series is in Arithmetic Series.

But in the above question , the series is in Harmonic Series.......

So u can't apply this formula to calculate the sum
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 [#permalink] New post 14 Oct 2006, 08:21
cicerone wrote:
Folks, u r doing a mistake here.

Sum of the series will be n/2 (a+l) provided the given series is in Arithmetic Series.

But in the above question , the series is in Harmonic Series.......

So u can't apply this formula to calculate the sum


Cicerone,
Is the formula to find out the sum of n terms of a harmonic series ln(n+1), where
l = last term
n =number of terms.

If so, answer would be
(1/66)*33*34 = 17
  [#permalink] 14 Oct 2006, 08:21
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