GMAT Practice Question Set #21 (Question 61-63)

Problem Solving Question #63: Chemical Air Ventillation  
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A chemical lab is scheduled to go through two air ventillation systems, a basic system and a more
advanced system that takes half an hour and two hours respectively to fully ventillate the room. If
both ventillation systems were to operate at the same time with thier respective constant rates,
how many hours would it take to fully ventilate the chemical lab?

(A)

1/4

(B)

1/3

(C)

2/5

(D)

5/4

(E)

3/2

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