Data Sufficiency

MI3 wrote:Q. If a car traveled from Townsend to Smallville at an average speed of 40 mph and then returned to Townsend later that evening, what was the average speed for the entire trip?
(1) The return trip took 50% longer than the trip there.
(2) The distance from Townsend to Smallville is 165 miles.

According to me, the answer should be A, am i correct?

Thanks,
M

Let the distance traveled = D miles
Time taken to travel from Townsend to Smallville = T1
Time taken to travel from Smallville to Townsend = T2
Average Speed = S
So, T1 = D/40

(1) T2 = T1 + T1/2 = 3T1/2 = (3/2)(D/40)
S = D/{D/40 + 3D/80}, which can be solved further to get the value of D; SUFFICIENT.

(2) The distance from Townsend to Smallville is 165 miles, but this is not sufficient to find S.

The correct answer is A.