BILL wrote:In the sequence of positive numbers X1, X2, X3....what is the value of X1?

(1) xi = (xi-1)/2 for all integers i>1
(2) x5 = x4/(x4+1)

source is GMAC practice test #1, answer is C

what am I missing?

its C

here it goes

statement 1. xi = (xi-1)/2 for all integers i>1

tells us nothing ............insufficient

statement 2. x5 = x4/(x4+1)

again nothing ..............insuffcient

combining together...

we know

xi = (xi-1)/2 thus X5 will be X4/2 ( Xi-1/2)..........................a
but statement 2 says X5 = x4/(x4+1).................................b

equate a and b

X4/2 = x4/(x4+1)

thus X4 = 1

now we can use this to find X1

thus C is the answer..

do let me know if u have any doubts...

Great explanation, thanks for the quick responce. Much appreciated