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# What is the range ans sum of of Sn Sn=

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SVP
Joined: 05 Jul 2006
Posts: 1519
Followers: 5

Kudos [?]: 115 [0], given: 39

What is the range ans sum of of Sn Sn= [#permalink]  13 Oct 2006, 12:58
What is the range ans sum of of Sn
Sn= 1/34+1/35+1/36+1/37......+1/66
Director
Joined: 23 Jun 2005
Posts: 847
GMAT 1: 740 Q48 V42
Followers: 5

Kudos [?]: 31 [0], given: 1

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.
Manager
Joined: 07 Jun 2006
Posts: 113
Followers: 2

Kudos [?]: 7 [0], given: 0

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

Anand, pls explain.
Director
Joined: 23 Jun 2005
Posts: 847
GMAT 1: 740 Q48 V42
Followers: 5

Kudos [?]: 31 [0], given: 1

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!
Senior Manager
Joined: 28 Aug 2006
Posts: 302
Followers: 10

Kudos [?]: 96 [0], given: 0

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
_________________
Director
Joined: 23 Jun 2005
Posts: 847
GMAT 1: 740 Q48 V42
Followers: 5

Kudos [?]: 31 [0], given: 1

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.

(1/66)*33*34 = 17
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# What is the range ans sum of of Sn Sn=

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