Find all School-related info fast with the new School-Specific MBA Forum

It is currently 12 Jul 2014, 13:53

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Population increase

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
BSchool Thread Master
avatar
Joined: 19 Feb 2010
Posts: 401
Followers: 18

Kudos [?]: 115 [0], given: 76

GMAT Tests User
Population increase [#permalink] New post 20 Sep 2010, 09:10
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

50% (02:10) correct 50% (00:49) wrong based on 8 sessions
The population of a certain town increases by 50 percent every 50 years. If the population in 1950 was 810, in what year was the population 160?

A. 1650
B. 1700
C. 1750
D. 1800
E. 1850
Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 18511
Followers: 3192

Kudos [?]: 21340 [0], given: 2546

Re: Population increase [#permalink] New post 20 Sep 2010, 09:20
Expert's post
cano wrote:
The population of a certain town increases by 50 percent every 50 years. If the population in 1950 was 810, in what year was the population 160?

A. 1650
B. 1700
C. 1750
D. 1800
E. 1850


Increase by 50% = times 1.5, so if the population at a certain year were 10 then in 50 years it would be 10*1.5 and in 50*2=100 years it would be 10*1.5*1.5=10*1.5^2 --> 160*1.5^n=810, where n is the # of 50-year periods --> (\frac{3}{2})^n=\frac{81}{16}=(\frac{3}{2})^4 --> n=4, so there were 4 50-year periods --> 1950-4*50=1750.

Answer: C.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Senior Manager
Senior Manager
User avatar
Joined: 25 Feb 2010
Posts: 459
Followers: 3

Kudos [?]: 30 [0], given: 5

GMAT Tests User
Re: Population increase [#permalink] New post 20 Sep 2010, 11:43
4 50 yrs to reach 810
_________________

GGG (Gym / GMAT / Girl) -- Be Serious

Its your duty to post OA afterwards; some one must be waiting for that...

Manager
Manager
User avatar
Joined: 29 Aug 2010
Posts: 156
Schools: Wharton/Lauder - Class of 2013
WE 1: Project Management, Telecommunications
Followers: 3

Kudos [?]: 19 [0], given: 16

GMAT Tests User
Re: Population increase [#permalink] New post 20 Sep 2010, 12:42
I just worked this one backwards until I reached 160. If the population increases by 50% then you're multiplying the previous number by 3/2. So to work backwards, divide by 3/2 (which is the same as multiplying by 2/3).

So we have:

1950: 810
1900: 810*(2/3) = 540
1850: 540*(2/3) = 360
1800: 360*(2/3) = 240
1750: 240*(2/3) = 160

Answer is C
BSchool Thread Master
avatar
Joined: 19 Feb 2010
Posts: 401
Followers: 18

Kudos [?]: 115 [0], given: 76

GMAT Tests User
Re: Population increase [#permalink] New post 20 Sep 2010, 16:50
redjam wrote:
I just worked this one backwards until I reached 160. If the population increases by 50% then you're multiplying the previous number by 3/2. So to work backwards, divide by 3/2 (which is the same as multiplying by 2/3).

So we have:

1950: 810
1900: 810*(2/3) = 540
1850: 540*(2/3) = 360
1800: 360*(2/3) = 240
1750: 240*(2/3) = 160

Answer is C


How long did it take you to work it like that?
Senior Manager
Senior Manager
avatar
Joined: 20 Jul 2010
Posts: 271
Followers: 2

Kudos [?]: 36 [0], given: 9

GMAT ToolKit User Reviews Badge
Re: Population increase [#permalink] New post 20 Sep 2010, 17:41
55 sec to work forward for C

160 -> 240 -> 360 -> 540 -> 810
_________________

If you like my post, consider giving me some KUDOS !!!!! Like you I need them

Manager
Manager
User avatar
Joined: 29 Aug 2010
Posts: 156
Schools: Wharton/Lauder - Class of 2013
WE 1: Project Management, Telecommunications
Followers: 3

Kudos [?]: 19 [0], given: 16

GMAT Tests User
Re: Population increase [#permalink] New post 21 Sep 2010, 05:35
cano wrote:
How long did it take you to work it like that?


Didn't specifically time myself but it wasn't longer than 2 mins. I would say around 1.5 mins. They are all numbers easily divisible by 3.
Re: Population increase   [#permalink] 21 Sep 2010, 05:35
    Similar topics Author Replies Last post
Similar
Topics:
Experts publish their posts in the topic If the population of a certain country increases at the rate Bunuel 3 09 Jun 2014, 05:45
2 Experts publish their posts in the topic The population of tigers in the National Park is increasing avaneeshvyas 4 15 Nov 2012, 00:13
Experts publish their posts in the topic It was an increase in the citys population that allowed the feruz77 7 18 Oct 2010, 22:58
population increase vcbabu 4 04 Jun 2009, 10:41
In the 1980s the rate of increase of the minority population gayathri 8 29 Nov 2004, 17:20
Display posts from previous: Sort by

Population increase

  Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group and phpBB SEO

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.