A certain culture of bacteria quadruples every hour. If a container with these bacteria was half full at 10:00 a.m., at what time was it one-eighth full?
(A) 9:00 a.m.
(B) 7:00 a.m.
(C) 6:00 a.m.
(D) 4:00 a.m.
(E) 2:00 a.m.
GMAT Question of the Day : Word Problem
Subscribe / Share
Article by Take GMAT Team
Authors bio is coming up shortly. 
A.
A
(A) 9:00 a.m
(A) 9:00 a.m.
a
Correct answer A.
a
Ans: a. At 10AM it was x/2 at 11am it will be (x/2)*4 = 2x and at 9AM is was (x/2)/4 = x/8.
A) Since it takes 1 hr to become 4 times so we can infer that it would also take 1 hr to become 1/4th. By reverse calculation, 1/2 can reduce to 1/8th, if we divide it by 4 in exactly 1 hr and that makes 9 AM the right answer.
A
A
A
Easy one. Clearly option A
A..
A