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March 5th, 2013, 03:45 AM  #1 
Newbie Joined: Mar 2013 Posts: 12 Thanks: 0  Sequence and series
Let Sn= 1 + 1/2 + 1/3 + ....+1/(2^n1), n belong to N then________ (a) S100<100 (b) S100> 100 (c) S200 = 100 (d) S200 > 200 Answer can be (A) but plz help me in its method so that I can understand it thoroughly. Thanks in advance. 
March 5th, 2013, 04:56 AM  #2  
Math Team Joined: Mar 2012 From: India, West Bengal Posts: 3,871 Thanks: 86 Math Focus: Number Theory  Re: Sequence and series Quote:
 
March 5th, 2013, 05:32 AM  #3 
Senior Member Joined: Feb 2013 Posts: 114 Thanks: 0  Re: Sequence and series
Can we also go like this : S_n ( of an A.P arithmetic progression ) as the given progression is H.P therefore there reciprocal is in A.P. where a is the first term of the series ; d is the common difference; n is the number of terms ; therefore putting these value in above we get : therefore its reciprocal gives you sum of H.P = 
March 5th, 2013, 05:37 AM  #4 
Math Team Joined: Mar 2012 From: India, West Bengal Posts: 3,871 Thanks: 86 Math Focus: Number Theory  Re: Sequence and series
As far as I know, harmonic series has no closed form expression, has it? 

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