neeti2711 wrote: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) 4:00 a.m.
(B) 5:00 a.m.
(C) 6:00 a.m.
(D) 7:00 a.m.
(E) 9:00 a.m.
Let the full container = 8 bacteria.
Since the container is half full at 10am, the number of bacteria at 10am = (1/2)8 = 4.
When the container is one-eighth full, the number of bacteria = (1/8)8 = 1.
Since the culture quadruples every hour, it takes one hour for the number of bacteria to increase from 1 to 4, implying that the container was one-eighth full at 9am.
The correct answer is
E.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at
[email protected].
Student Review #1
Student Review #2
Student Review #3
