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by ST » Tue May 26, 2009 5:56 am
could someone explain attached problem?

Thank you

ST
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by ssmiles08 » Tue May 26, 2009 6:07 am
Let's take a1 = x, a2 = 2x, a3 = 4x, a4 = 8x, a5 = 16x

a5 - a2 = 12

16x - 2x = 12; 14x = 12

x = 6/7

since a1 = x; a1 = 6/7
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by bluementor » Tue May 26, 2009 6:07 am
each term after the first is equal to twice the previous term

this simply means that a5 = 2*a4, a4 = 2*a3 and so on...

a5 - a2 = 12
2*(a4) - 2*(a1) = 12
2*2*(a3) - 2*(a1) = 12
4*2*(a2) - 2*(a1) = 12
8*2*(a1) - 2*(a1) = 12
16*(a1) - 2*(a1) = 12
14*(a1) = 12
a1 = 12/14 = 6/7

choose E.

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thank you

by ST » Tue May 26, 2009 6:13 am
now i understand.
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