Consider the sequence 1, -2, 3, -4, 5, -6, ..... , whose n-th term is [(-1)^(n+1)]*(n). What is the average of the first 200 terms of the sequence?
A) -1
B) -0.5
C) 0
D) 0.5
E) 1
A) -1
B) -0.5
C) 0
D) 0.5
E) 1
Note that the sum of alternate pairs of the series taken in order is -1.diehard_gmat wrote:Consider the sequence 1, -2, 3, -4, 5, -6, ..... , whose n-th term is [(-1)^(n+1)]*(n). What is the average of the first 200 terms of the sequence?
A) -1
B) -0.5
C) 0
D) 0.5
E) 1
There are 100 such pairs in the first 200 terms. Sum of each pair is -1.
Hence, sum of 200 terms = (-1)*(100) = -100
Hence, average = (-100)/200 = -0.5
The correct answer is B
