X(j) is the jth term in the sequence, as we say X(2) is the 2nd term and so on.dreamv wrote:This was on GMATPrep. It's confusing to me what is asking for.. What is Xj here? Please help..
(1) X(j) = X(j - 1)/2 for j > 1 implies that every term is one-half of the previous term. Example: X(2) = X(1)/2 but we cannot find X(1) from here; NOT sufficient.
(2) X(5) = X(4)/[X(4) + 1] is again NOT sufficient to find X(1); NOT sufficient.
Combining (1) and (2), since X(j) = X(j - 1)/2, so X(5) = X(4)/2
So, X(4)/2 = X(4)/[X(4) + 1]
1/2 = 1/[X(4) + 1]
2 = X(4) + 1
x(4) = 1, so we can find X(3), X(2) and hence find X(1) using this; SUFFICIENT.
The correct answer is C.
