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by sudhirsk » Sun Jul 01, 2007 12:41 pm
How to solve this?
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by jayhawk2001 » Sun Jul 01, 2007 4:36 pm
The terms are 1/2, -1/4, 1/8, -1/16 ... etc.

Sum = 1/2 (1 - 1/2 + 1/4 - 1/8 ... 10 terms)

The sum of terms inside the paranthesis is > 1/2 and < 1

So, product > 1/4 and < 1/2

Hence D
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by sudhirsk » Sun Jul 01, 2007 5:20 pm
Thanks Jay.
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by maolivie » Mon Jul 02, 2007 7:00 am
why did you calculate the sum by multiplying everythign in the parenthesis by 1/2? if it's asking for some I normally think add all output for that sequence. Is there some sort of trick to this?
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by givemeanid » Mon Jul 02, 2007 7:24 am
The sequence is 1/2 - 1/4 + 1/8 - 1/16 + 1/32...
The first two terms amount to 1/2 - 1/4 = 1/4.
Realize that the terms after than keep getting smaller and they will never amount to 1/4. They will be positive since 1/8 is +ve(the beginning is +ve and is less than 1/4).
So, the result will 1/4 + something. So, it will be greater than 1/4 and less than 1/2.
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