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Math Query ?

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Manager
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Joined: 14 Oct 2008
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Math Query ? [#permalink]

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New post 14 Oct 2008, 06:44
In the Infinite Sequence a1 , a2, a3, a4 .. aN. each term after the first is equal to twice the previous term. If a5-a2 = 12 , what is the value of a1 ?

a. 4
b. 24 / 7
c. 2
d. 12 / 7
e. 6 / 7

Can you tell me which is the right answer ? and how ? I got it wrong and I am not able to find how to get to the right one ..

Cheers.

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Manager
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Joined: 25 Aug 2008
Posts: 220

Kudos [?]: 72 [0], given: 5

Location: India
WE 1: 3.75 IT
WE 2: 1.0 IT
Re: Math Query ? [#permalink]

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New post 14 Oct 2008, 07:43
According to the question each term after the first is equal to twice the previous term.

Let first term be a1.
then a2 = 2a1
a3=2a2 = 4a1
a4=8a1
a5=16a1

a5 - a2 = 12
=>16a1 - 2a1 = 12
=>14a1 = 12
=>a1 = 12/14 = 6/7.

E is answer.

Wat say?? :-D
_________________

Cheers,
Varun


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Re: Math Query ? [#permalink]

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New post 14 Oct 2008, 07:54
On the point. I can't believe, i did'nt do that myself :-(
Cheers, anyways.

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Re: Math Query ?   [#permalink] 14 Oct 2008, 07:54
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