Events & Promotions
|
|
GMAT Club Daily Prep
Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.
Customized
for You
Track
Your Progress
Practice
Pays
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Apr 1612:00 PM EDT
-11:59 PM EDT
You’re first to know: Save $200 on GMAT prep starting tomorrow, 4/13. Get 6 official practice tests and study with real questions. Be ready to save!
Apr 2610:00 AM EDT
-11:00 AM EDT
The Target Test Prep course represents a quantum leap forward in GMAT preparation, a radical reinterpretation of the way that students should study. Try before you buy with a 5-day, full-access trial of the course for FREE!
Apr 2711:00 AM EDT
-12:00 PM EDT
Prefer video-based learning? The Target Test Prep OnDemand course is a one-of-a-kind video masterclass featuring 400 hours of lecture-style teaching by Scott Woodbury-Stewart, founder of Target Test Prep and one of the most accomplished GMAT instructors
Apr 2808:00 AM PDT
-11:00 AM PDT
Whether you are just beginning your MBA journey or fine-tuning your path to a 700+ score, GMAT Day is designed to give you a competitive edge.
22 Dec 2025, 09:00
Kudos
Bookmarks
E
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!
Difficulty:
85%
(hard)
Question Stats:
71% (02:11) correct
29%
(03:02)
wrong
based on 190
sessions
History
Date
Time
Result
Not Attempted Yet
A culture of bacteria had a population of 8,000 at 10 AM. The population grew at a fixed percentage rate per hour and reached 64,000 at 7 PM on the same day. If the population continues to grow at that same rate, at what time will the population reach 256,000?
A. 9 PM of the same day
B. 10 PM of the same day
C. 12 AM of the next day
D. 12:30 AM of the next day
E. 1 AM of the next day
M46-17
A. 9 PM of the same day
B. 10 PM of the same day
C. 12 AM of the next day
D. 12:30 AM of the next day
E. 1 AM of the next day
M46-17
12 Days of Christmas Competition
This question is part of our holiday event
Win $40,000 in prizes: courses, tests, and more
22 Dec 2025, 10:00
Kudos
Bookmarks
Bunuel
GMAT Club Official Explanation:
In 9 hours, from 10 AM to 7 PM, the population grew by a factor of 8 (64,000/8,000 = 8).
Since the rate of growth is constant, the population doubles every 3 hours: 2 * 2 * 2 = 8 over 3 + 3 + 3 = 9 hours. The same rate of increase (* 2) in the same time period (3 hours).
Therefore, to grow 4 times (from 64,000 to 256,000), the population will need an additional 6 hours (3 hours + 3 hours).
Hence, the population will reach 256,000 at 7 PM + 6 hours = 1 AM of the next day.
Answer: E.
Alternatively, here is the algebraic approach.
Given:
\(8,000 * r^9 = 64,000\)
\(r = \sqrt[9]{8}= \sqrt[9]{2^3} =\sqrt[3]{2} \)
We need to find such x, where x is the number of hours needed from 10 AM for the population to reach 256,000, such that:
\(8,000 * r^x = 256,000\)
\(r^x = 32\)
\(( \sqrt[3]{2})^x = 32\)
\(2^{\frac{x}{3}} = 2^5\)
\(\frac{x}{3}=5\)
\(x = 15\)
Thus, after 15 hours from 10 AM (which is 1 AM of the next day), the population will reach 256,000.
Answer: E.
General Discussion
22 Dec 2025, 09:19
Kudos
Bookmarks
Let the fixed rate be x
8000 * x^9 = 64000
x^9 = 2^3
x = 2^(1/3)
Let number of hours to grow from 64000 to 256000 be n
64000 * {2^(1/3)}n = 256000
2^n/3 = 4
2^n = 4^3
2^n = 2^6
n = 6hours
7PM + 6hours = 1 AM
Answer E
8000 * x^9 = 64000
x^9 = 2^3
x = 2^(1/3)
Let number of hours to grow from 64000 to 256000 be n
64000 * {2^(1/3)}n = 256000
2^n/3 = 4
2^n = 4^3
2^n = 2^6
n = 6hours
7PM + 6hours = 1 AM
Answer E
Bunuel
