VyDinh wrote:I have this question from GMAT Pretest - test 2
In the sequence of positive numbers x1, x2, x3,..., what is the value of x1?
1. xi = (xi-1)/2 for all integer i>1 (to clarify i.e x3=x2/2)
2. x5 = x4/(x4 + 1)
OA is C
Neither statement alone is sufficient to determine the value of x�.
Statements combined:
Statement 1 implies that xâ‚… = xâ‚„/2.
Statement 2 indicates that xâ‚… = xâ‚„/(xâ‚„ + 1).
Thus:
xâ‚„/2 = xâ‚„/(xâ‚„ + 1)
Since the numerators are equal, so must be the denominators:
2 = xâ‚„ + 1
xâ‚„ = 1.
Using the value of x₄, we can apply the formula in statement 1 to determine x₃, x₂, and x�.
SUFFICIENT.
The correct answer is
C.
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