Hello,
Can you please assist with this:
In a sequence of positive integers, every
term after the second equals the sum of the
two preceding ones if the sum is odd and
one-half the sum of the two preceding terms
if the sum is even. If the fourth term in the
sequence is 7 and the fifth is 5, which is the
first term in the sequence?
(A) 14
(B) 10
(C) 4
(D) 3
(E) 2
OA: E
I tried to proceed as follows:
S5 = 5 = odd => S5 = S4 + S3 => 5 = 7 + S3 = > S3 = -2
S4 = 7 = odd => S4 = S3 + S2 => 7 = (-2) + S2 => S2 = 9
S3 = -2 = even => S3 = 1/2 ( S2 + S1 ) = 1/2 ( 9 + S1 ) => -4 = 9 + S1 => S1 = -13
However, this answer is obviously wrong. Can you please assist? Thanks a lot - Sri
Can you please assist with this:
In a sequence of positive integers, every
term after the second equals the sum of the
two preceding ones if the sum is odd and
one-half the sum of the two preceding terms
if the sum is even. If the fourth term in the
sequence is 7 and the fifth is 5, which is the
first term in the sequence?
(A) 14
(B) 10
(C) 4
(D) 3
(E) 2
OA: E
I tried to proceed as follows:
S5 = 5 = odd => S5 = S4 + S3 => 5 = 7 + S3 = > S3 = -2
S4 = 7 = odd => S4 = S3 + S2 => 7 = (-2) + S2 => S2 = 9
S3 = -2 = even => S3 = 1/2 ( S2 + S1 ) = 1/2 ( 9 + S1 ) => -4 = 9 + S1 => S1 = -13
However, this answer is obviously wrong. Can you please assist? Thanks a lot - Sri
