Hi rakeshd347,

This DS question can be easily solved with a bit of "probability math" and a bit of TESTing Values.

We're told that there are 36 socks, but we are told NOTHING about their color(s). The question asks if we pull 2 socks, what is the probability that they're both black.

Fact 1: Probability that first sock pulled is black is 4/9. We can figure out the total number of black socks:

36(4/9) = 16 black socks. This would give us enough information to calculate the probability of 2 black socks pulled:

(16/36)(15/35) = one answer; no reason to do the math.
Fact 1 is SUFFICIENT.

Fact 2: The Number of White socks is 4 more than the Number of Black socks.

W = B + 4

If W = 4, B = 0, the probability of pulling 2 black socks is 0

If W = 6, B = 2, the probability of pulling 2 black socks is something other than 0
Fact 2 is INSUFFICIENT

Final Answer: A

GMAT assassins aren't born, they're made,
Rich