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

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

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New post 24 Mar 2008, 13:41
10
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A
B
C
D
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Question Stats:

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

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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.
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Director
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Re: What was the percent increase in the population of City K from 1980 to  [#permalink]

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New post 24 Mar 2008, 14:57
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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.

As statement 2 alone can answer the question, so Answer B.
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Re: What was the percent increase in the population of City K from 1980 to  [#permalink]

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New post 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
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Re: What was the percent increase in the population of City K from 1980 to  [#permalink]

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New post 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..
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Re: What was the percent increase in the population of City K from 1980 to  [#permalink]

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New post 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

Answer is B.
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Re: What was the percent increase in the population of City K from 1980 to  [#permalink]

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New post 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)
Hence, answer C
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Re: What was the percent increase in the population of City K from 1980 to  [#permalink]

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New post 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

Answer: B

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Brent
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Re: What was the percent increase in the population of City K from 1980 to   [#permalink] 01 Dec 2019, 18:10
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