Last visit was: 19 Jul 2025, 10:49 It is currently 19 Jul 2025, 10:49
Home
GMAT
Messages
Tests
Schools
Events
Rewards
Chat
My Profile
Close
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

we will pick new questions that match your level based on your Timer History

Track
Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History
Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.
Go to My Error Log Learn more
Close
Request Expert Reply
Confirm Cancel
Back to Forum
Create Topic
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 19 July 2025
Posts: 102,622
Own Kudos:
742,741
 [2]
Given Kudos: 98,235
Products:
GMAT Club Tests Forum Quiz
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 102,622
Kudos: 742,741
 [2]
The population of City X doubles every 25 years. If this rate continue 06 Apr 2017, 01:42
Kudos
Add Kudos
2
Bookmarks
Bookmark this Post
00:00
Start Timer
Pause Timer
Resume Timer
Show Answer
Hide
Show
History
E
Be sure to select an answer first to save it in the Error Log before revealing the correct answer (OA)!

Difficulty:

25% (medium)

Question Stats:

77% (01:38) correct 23% (01:56) wrong based on 111 sessions

History

Date
Time
Result
Not Attempted Yet
The population of City X doubles every 25 years. If this rate continues for the foreseeable future, how many centuries will it take for the population to increase from 20,000 to 1,280,000?

A. 6
B. 4.5
C. 2.5
D. 2
E. 1.5
ShowHide Answer
Official Answer
E
User avatar
0akshay0
User avatar
Joined: 19 Apr 2016
Last visit: 14 Jul 2019
Posts: 194
Own Kudos:
622
 [1]
Given Kudos: 59
Location: India
Schools: Jindal '20 Kelley '20 Broad '20 Carey '20 Mays '20
GMAT 1: 570 Q48 V22
GMAT 2: 640 Q49 V28
GPA: 3.5
WE:Web Development (Computer Software)
Schools: Jindal '20 Kelley '20 Broad '20 Carey '20 Mays '20
GMAT 2: 640 Q49 V28
Posts: 194
Kudos: 622
 [1]
The population of City X doubles every 25 years. If this rate continue 06 Apr 2017, 03:20
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
The population of City X doubles every 25 years. If this rate continues for the foreseeable future, how many centuries will it take for the population to increase from 20,000 to 1,280,000?

A. 6
B. 4.5
C. 2.5
D. 2
E. 1.5

20000---after 25 years---40000---after 25 years---80000---after 25 years---160000---after 25 years---320000---after 25 years---640000---after 25 years---1280000

so from 20000 to 1280000 it takes 25*6 years i.e. 150 years = 1.5 centuries

Hence option E is correct
Hit Kudos if you liked it 8-)
User avatar
Kurtosis
User avatar
Current Student
Joined: 13 Apr 2015
Last visit: 10 Nov 2021
Posts: 1,400
Own Kudos:
4,987
Given Kudos: 1,228
Location: India
Products:
My Reviews
Posts: 1,400
Kudos: 4,987
The population of City X doubles every 25 years. If this rate continue 06 Apr 2017, 07:01
Kudos
Add Kudos
Bookmarks
Bookmark this Post
1,280,000/20,000 = 64 times = 2^6 times

25*6 = 150 years = 1.5 centuries

Answer: E
User avatar
eddy8700
User avatar
Joined: 25 Jan 2016
Last visit: 02 Oct 2020
Posts: 87
Own Kudos:
75
Given Kudos: 12
Status:active
Location: India
Concentration: Finance, Entrepreneurship
Schools: Rotman '19 Insead Sept'18 Booth '19
GPA: 4
WE:Web Development (Computer Software)
Schools: Rotman '19 Insead Sept'18 Booth '19
Posts: 87
Kudos: 75
The population of City X doubles every 25 years. If this rate continue 06 Apr 2017, 08:14
Kudos
Add Kudos
Bookmarks
Bookmark this Post
answer is E


20000*2^n=1280000

2^n=64
n=6

it takes 25 years to double
6 times will take 25*6=150/100=1.5 centuries
User avatar
ScottTargetTestPrep
User avatar
Target Test Prep Representative
Joined: 14 Oct 2015
Last visit: 18 Jul 2025
Posts: 21,145
Own Kudos:
26,204
 [1]
Given Kudos: 296
Status:Founder & CEO
Affiliations: Target Test Prep
Location: United States (CA)
Expert
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 21,145
Kudos: 26,204
 [1]
The population of City X doubles every 25 years. If this rate continue 12 Apr 2017, 12:05
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Bunuel
The population of City X doubles every 25 years. If this rate continues for the foreseeable future, how many centuries will it take for the population to increase from 20,000 to 1,280,000?

A. 6
B. 4.5
C. 2.5
D. 2
E. 1.5


We are given that the population of City X doubles every 25 years. We need to determine the number of centuries it will take the population to increase from 20,000 to 1,280,000.

We can start by making a list (or table) that keeps track of doubling the population every 25 years:

Current: 20,000
After 25 years: 40,000
After 50 years: 80,000
After 75 years: 160,000
After 100 years: 320,000
After 125 years: 640,000
After 150 years: 1,280,000

Thus it takes 150 years, or 1.5 centuries, to increase the population from 20,000 to 1,280,000.

Answer: E
User avatar
bumpbot
User avatar
Non-Human User
Joined: 09 Sep 2013
Last visit: 04 Jan 2021
Posts: 37,447
Own Kudos:
1,013
Posts: 37,447
Kudos: 1,013
The population of City X doubles every 25 years. If this rate continue 09 Jan 2024, 13:17
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
Moderators:
Bunuel
Math Expert
102620 posts
Krunaal
PS Forum Moderator
698 posts