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Sequence

by teejaycrown » Fri Nov 02, 2012 9:52 pm
In the sequence of positive number x1, x2, x3,.......what is the value of xi

1 x1 = xi -1 /2 for all integers i > 1

2 x5 = x4/x4+1
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by GMATGuruNY » Sat Nov 03, 2012 1:42 am
The question has been transcribed incorrectly. Here is the actual question:
In the sequence of positive numbers X�, X₂, X₃....what is the value of X�?

(1) Xⅈ = (Xⅈ-�)/2 for all integers ͥͥⅈ > 1

(2) Xâ‚… = Xâ‚„/(Xâ‚„+1)
Neither statement alone is sufficient.

Combined:
In statement 2, Xâ‚… = Xâ‚„/(Xâ‚„+1).
In statement 1, when â…ˆ=5, Xâ‚… = Xâ‚„/2.

In each equation, the righthand side is equal to Xâ‚….
Equating the righthand sides, we get:
Xâ‚„/(Xâ‚„+1) = Xâ‚„/2
Xâ‚„+1 = 2
Xâ‚„ = 1.

Since statement 1 indicates that each term is 1/2 the preceding term, we get:
X₃ = 2
Xâ‚‚ = 4
X� = 8.
SUFFICIENT.

The correct answer is C.
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