Data Sufficiency

Can someone kindly explain this?

tanyajoseph wrote:Can someone kindly explain this?

looks like the following values would fit the sequence... going upto a ( 8 )

a(0) = 0
a(1) = 1
a(2) = -1
a(3) = 3
a(4) = -3
a(5) = 5
a(6) = -5
a(7) = 7
a ( 8 ) = -7

Statement (1): If n is odd, terms upto n-1 (n-1 is even) would cancel each other out and the sum would be positive
Statement (1) is sufficient

Statement (2): For a(n) to be positive, n has to be odd. The previous argument then applies. Sufficient.

Answer [D], each alone.

but what if A1 = minus 3 .... Then, answer would have to be C no?

Why do u assume A1 to be positive if it is not told anywhere?

a1 can never be -3. it is not an assumption

as it is said a(k) = k, a(1) = 1

>but what if A1 = minus 3 .... Then, answer would have to be C no?

No.

a1 != -3 by definition

ak = k, if k is odd
so a1 = 1 and 1 only!

can u tell me source of this practise test..people post lot many questions from these tests.

Its from a source called Power Prep - found in MBA.com