testprep2010 wrote:
In the sequence of positive numbers \(x_1\), \(x_2\), \(x_3\), ..., what is the value of \(x_1\)?
(1) \(x_i=\frac{x_{(i-1)}}{2[/fraction
(2) [m]x_5=[fraction]x_4/x_4+1}\)
This is not my strongest topic, but I just want to share my experience with this type of questions.
One can solve this type of questions if you have a general formula (sometimes given in the question stem) and concrete values for at least two other terms in the sequence.
Question: We are not given any formula here, we are just asked to find a value of X1.
(1) It's just a general formula, that gives us the relaionship of any two terms in the sequence, but we don't have any concrete values. Not sufficient
(2) Here we are given ONLY a relationship between X5 and X4, but you cannot just use this relationship for other terms, X4 and X5 could by any positive values. Not sufficient.
(1) + (2): x
4=x
4/x
4+1 = x
4/2, ok, so you can find the x
4, in the same manner you can find x
3 etc. so ,
STOP, there is no need to calculate further, one can see here, that it's possible to find x
1Answer C
Would appreciate some comments from math experts. I have seen many questions of this type, and there are always about a general formula and some concrete values, which we can use to find any term in the sequence.