One night a certain hotel rented 1/2 of its rooms, including 2/3 of their air conditioned rooms. If 3/5 of its rooms were air conditioned, what percent of the rooms that were not rented were air conditioned? Options
A) 25%	B) 30%	C) 35%	D) 40%	E) 50%
The rooms which were not rented is 1/2   The AC rooms which were not rented is (1/3)*(3/5) = 1/5   The percentage of unrented rooms which were AC rooms is (1/5) / (1/2) = 2/5 = 40%   The answer is 40%.
<result>D</result>
One night a certain hotel rented 1/2 of its rooms, including 2/3 of their air conditioned rooms. If 3/5 of its rooms were air conditioned, what percent of the rooms that were not rented were air conditioned?