GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 05 Dec 2019, 23:42

### 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

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

# What was the percent increase in the population of City K from 1980 to

Author Message
TAGS:

### Hide Tags

Director
Joined: 01 May 2007
Posts: 644
What was the percent increase in the population of City K from 1980 to  [#permalink]

### Show Tags

24 Mar 2008, 13:41
10
37
00:00

Difficulty:

15% (low)

Question Stats:

76% (01:00) correct 24% (00:48) wrong based on 540 sessions

### HideShow timer Statistics

What was the percent increase in the population of City K from 1980 to 1990 ?

(1) In 1970 the population of City K was 160,000
(2) In 1980 the population of City K was 20 percent greater than it was in 1970, and in 1990 the population of City K was 30 percent greater than it was in 1970.
Director
Joined: 10 Sep 2007
Posts: 655
Re: What was the percent increase in the population of City K from 1980 to  [#permalink]

### Show Tags

24 Mar 2008, 14:57
13
7
Statement 1:
Tells us about population in 1970 and nothing else, so this alone is insufficient.

Statement 2:
Tells us that in 1980 population is 20% more than it was in 1970. Say it was x in 1970, then in 1980 it is 1.2x.
Also given that in 1990 population is 30% more than it was in 1970. Say it was x in 1970, then in 1990 it is 1.3x.

Percent Increase from 1980 to 1990 = (1.3x-1.2x)*100/1.2x (Although you don't need to calcluate it, as answer is not required to be filled in anywhere.

##### General Discussion
Senior Manager
Status: No dream is too large, no dreamer is too small
Joined: 14 Jul 2010
Posts: 409
Re: What was the percent increase in the population of City K from 1980 to  [#permalink]

### Show Tags

28 Jun 2011, 11:07
4
Let the population of 1970 = 100
so population of 1980 = 120
thus population of 1990 = 130
percentage increase = 10/120*100
ans.D
_________________
Intern
Joined: 28 Feb 2011
Posts: 46
Re: What was the percent increase in the population of City K from 1980 to  [#permalink]

### Show Tags

28 Jun 2011, 18:51
1
1
B..
Let population in 1970=100
Then, in 1980= 120
in 1990= 130

We can easily find the percent increase from 1980 to 1990 now..
_________________
Fight till you succeed like a gladiator..or doom your life which can be invincible
Director
Joined: 01 Feb 2011
Posts: 531
Re: What was the percent increase in the population of City K from 1980 to  [#permalink]

### Show Tags

28 Jun 2011, 16:10
1
((90 - 80 )/ 80 )*100

1. Not sufficient

we dont know anything about 80 or 90.

2. Sufficient

70 80 90
x 120x/100 130x/100

from this we can easily find out ((80-90)/80 )*100

Intern
Joined: 12 Jul 2016
Posts: 17
Re: What was the percent increase in the population of City K from 1980 to  [#permalink]

### Show Tags

08 May 2017, 03:45
Statement 1 is clearly unsufficient since there is no information about 1980 nor 1990.
Statement 2 ables to deduce the solution but only if we have the 1970's population. (unsufficient)
GMAT Club Legend
Joined: 12 Sep 2015
Posts: 4121
Re: What was the percent increase in the population of City K from 1980 to  [#permalink]

### Show Tags

01 Dec 2019, 18:10
Top Contributor
jimmyjamesdonkey wrote:
What was the percent increase in the population of City K from 1980 to 1990 ?

(1) In 1970 the population of City K was 160,000
(2) In 1980 the population of City K was 20 percent greater than it was in 1970, and in 1990 the population of City K was 30 percent greater than it was in 1970.

Target question: What was the percent increase in the population of City K from 1980 to 1990 ?

Statement 1: In 1970 the population of City K was 160,000
Since we're given no information about the population in 1980 or 1990, it's impossible to answer the target question.
Statement 1 is NOT SUFFICIENT

Statement 2: In 1980 the population of City K was 20 percent greater than it was in 1970, and in 1990 the population of City K was 30 percent greater than it was in 1970.
Let x = the population in 1970
So, 1.2x = the population in 1980
And 1.3x = the population in 1990

Percent increase = (100)(1990 population - 1980 population)/(1980 population)
= (100)(1.3x - 1.2x)/(1.2x)
= (100)(0.1x)/(1.2x)
= 10/1.2
So, the percent increase = 10/1.2 percent (we need not actually evaluate the actual fraction)

Since we can answer the target question with certainty, statement 2 is SUFFICIENT

Cheers,
Brent
_________________
Test confidently with gmatprepnow.com
Re: What was the percent increase in the population of City K from 1980 to   [#permalink] 01 Dec 2019, 18:10
Display posts from previous: Sort by