This is my take on these problems IMHO

(1) The arrangement is of the form


G B G
______
| |
______
B G B

So the guys can sit in 3! ways and the girls can sit in 3! ways and hence total num of ways = 3!*3! i.e. 36
(I am not 100% sure about this problem though)

(2) The first condition tells is that x < 1 but does not tell us anything beyond that so insufficient
The second condition tells that x > 0. But still in sufficient
Combining them yields 0 < x < 1 which is sufficient hence C

(3) Well tossed three times and lands the same side is the same as HHH or TTT so the probability is (1/2) * (1/2) * (1/2) + (1/2)* (1/2) * (1/2) = 1/4

(4) Ans is D because the total pay for the worker is 5x + 50 (x + x + 5...X + 20). Now the first condition compares two pays and we can solve x from that and hence obtain total pay
Same thing with second condition too so both are independently sufficient

Hey astacio

I saw that u scored 540 in GMAT ,i just wanted to know what was the break-up
and do u feel any similarity between GMATPrep exams and the actual
gmat???

I have been scoring in the same range!!!

Just curious