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Source: — Data Sufficiency |
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Re: I need help

by jayhawk2001 » Fri May 18, 2007 4:36 pm
rajt wrote:Can you help me solve this?
You have to see the pattern here

(-1)^2*1/2 + (-1)^3*1/2^2 + ... + (-1)^11* 1/2^10

Take all positive and negative values separately

1/2 (1 + 1/2^2 + ... + 1/2^8 ) - 1/2^2 * (1 + 1/2^2 + ... + 1/2^8 )

= (1/2 - 1/4) * (1 + 1/2^2 + ... + 1/2^8 )
= 1/4 * (1 + 1/2^2 + ... + 1/2^8 )

This is greater than 1/4 but less than 1/2

Is it D ?
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by rajt » Fri May 18, 2007 7:22 pm
yes the answer is D. Your explanation is pretty clear.
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