A chemical lab is scheduled to go through two air ventilation systems, a basic system and a more advanced system that takes forty minutes and 3 hours respectively to fully ventilate the room. If both ventilation systems were to operate at the same time with their respective constant rates, how many hours would it take to fully ventilate the chemical lab?
Choose the correct choice from the following options
A) 4/9  B) 2/3  C) 7/12  D) 6/11  E) 3/5
The rate of the basic system is 1 room/ (2/3 of an hour) = 3/2 rooms per hour   The rate of the advanced system is 1/3 of a room per hour   The combined rate is 11/6 rooms per hour.   The time to ventilate one room is 6/11 of an hour.   The answer is 6/11.
<result>D</result>
A chemical lab is scheduled to go through two air ventilation systems, a basic system and a more advanced system that takes forty minutes and 3 hours respectively to fully ventilate the room. If both ventilation systems were to operate at the same time with their respective constant rates, how many hours would it take to fully ventilate the chemical lab?