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Please explain the calculation with usage of AP and GP formu

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by Uva@90 » Sat Nov 23, 2013 11:25 pm
[email protected] wrote:1+ 2.2^1 + 3.2^2 + 4.2^3 + ... + 100.2^99 = ?

A) 100.2^100
B) 99.2^100 + 1
C) 99.2^99 + 99
D) 2^100
The Sequence is 1+ 2.2^1 + 3.2^2 + 4.2^3 + ... + 100.2^99

EVEN+ODD = ODD
So,1+ 2.2^1 + 3.2^2 + 4.2^3 + ... + 100.2^99
In the above sequence highlighted with green one is even.
1+Even should be ODD
Eliminate A and D

Take the last term of the sequence 100.2^99
2^99(99+1) = > 99.2^99 +2^99 > Option C
Eliminate C.

Only option left is B.

So Answer should be B

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by Uva@90 » Sat Nov 23, 2013 11:27 pm
Apart from the question,

Shibriz,
Will GMAT question have only 4 Options.(A,B,C,D) ? There should be 5 na ?

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by [email protected] » Sun Nov 24, 2013 5:15 pm
Hi Uva@90,

This is NOT a GMAT question. While some of the concepts (exponents, sequences) are on the GMAT, they're not going to be in this arrangement.

GMAT assassins aren't born, they're made,
Rich
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