exponents

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exponents

by grandh01 » Thu Aug 23, 2012 7:07 pm
1/2^10+1/2^11+1/2^12+1/2^12=?

1) 1/2^7
2) 1/2^8
3) 1/2^9
4) 1/2^13
5) 1/2^45

OA is C

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by Anurag@Gurome » Thu Aug 23, 2012 7:26 pm
grandh01 wrote:1/2^10+1/2^11+1/2^12+1/2^12=?

1) 1/2^7
2) 1/2^8
3) 1/2^9
4) 1/2^13
5) 1/2^45

OA is C
1/2^10 + 1/2^11 + 1/2^12 + 1/2^12
= 1/2^10(1 + 1/2 + 1/2² + 1/2²)
= 1/2^10(1 + 1/2 + 1/4 + 1/4)
= 1/2^10(1 + 1/2 + 1/2)
= 1/2^10(1 + 1)
= 2/2^10
= [spoiler]1/2^9[/spoiler]

The correct answer is C.
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