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Percentage increase question

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by vittalgmat » Sun May 03, 2009 7:43 pm
Hi folks,
This could be tricky problem, if one doesnt pay attention....
Here are two versions. Pls comment on this.

Version 1:
-------------
What is the % increase in population of City K from 1980 to 1990?
a. In 1970 population of K was 160,000
b. In 1980 population of K was 20% greater than 1970 and in 1990 population is 30% greater than in 1970


Version 2:
--------------
What is the % increase in population of City K from 1980 to 1990?
a. In 1970 population of K was 160,000
b. In 1980 population of K was 20% greater than 1970 and in 1990 population is 30% greater than in 1980
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Re: Percentage increase question

by btg760 » Sun May 03, 2009 7:56 pm
vittalgmat wrote:Hi folks,
This could be tricky problem, if one doesnt pay attention....
Here are two versions. Pls comment on this.

Version 1:
-------------
What is the % increase in population of City K from 1980 to 1990?
a. In 1970 population of K was 160,000
b. In 1980 population of K was 20% greater than 1970 and in 1990 population is 30% greater than in 1970


Version 2:
--------------
What is the % increase in population of City K from 1980 to 1990?
a. In 1970 population of K was 160,000
b. In 1980 population of K was 20% greater than 1970 and in 1990 population is 30% greater than in 1980
The answer of version 1 should be (C) and answer for version 2 should be (B).
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by lilu » Sun May 03, 2009 8:20 pm
I think the answer to both versions of the question is B

First version:
Let 1970=100
Then, 1980=100*1.2=120
And 1990=100*1.3=130
And the % increase from '80 to '90 is 120/130~9.2%


Second version:
Let 1970=100
Then, 1980=100*1.2=120
And 1990=120*1.3=156
And the % increase from '80 to '90 is 120/156~7.6%

B in both cases
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Re: Percentage increase question

by Vemuri » Sun May 03, 2009 8:23 pm
vittalgmat wrote: Version 1:
-------------
What is the % increase in population of City K from 1980 to 1990?
a. In 1970 population of K was 160,000
b. In 1980 population of K was 20% greater than 1970 and in 1990 population is 30% greater than in 1970
%increase = (pop of(1990)-pop of(1980))/pop of(1980)

Stmt1: Insufficient
Stmt2: pop of 1980 = pop of 1970(1+1/5) ==> (6/5) pop of 1970
pop of 1990 = pop of 1970(1+3/10) ==> (13/10) pop of 1970

From this we can determine the % increase ==> pop of 1970( 13/10 - 6/5)/(6/5) pop of 1970 ==> 1/12 ==> ~8% increase
vittalgmat wrote: Version 2:
--------------
What is the % increase in population of City K from 1980 to 1990?
a. In 1970 population of K was 160,000
b. In 1980 population of K was 20% greater than 1970 and in 1990 population is 30% greater than in 1980
%increase = (pop of(1990)-pop of(1980))/pop of(1980)

Stmt1: Insufficient
Stmt2: pop of 1980 = pop of 1970(1+1/5) ==> (6/5) pop of 1970
pop of 1990 = pop of 1980(1+3/10) ==> (13/10) pop of 1980 ==> (13/10)(6/5) pop of 1970

From this we can determine the % increase ==> pop of 1970( (13/10)(6/5) - 6/5)/(6/5) pop of 1970 ==> (3/10) ==> ~8% increase
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by vittalgmat » Sun May 03, 2009 9:43 pm
Thanks for the replies.
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by missrochelle » Wed Sep 01, 2010 9:44 am
lilu wrote:I think the answer to both versions of the question is B

First version:
Let 1970=100
Then, 1980=100*1.2=120
And 1990=100*1.3=130
And the % increase from '80 to '90 is 120/130~9.2%


Second version:
Let 1970=100
Then, 1980=100*1.2=120
And 1990=120*1.3=156
And the % increase from '80 to '90 is 120/156~7.6%

can someone explain how you use #s on this example, when they don't give you numbers to use --- how can u make these assumptions? if we let 1970 = 100 ,is it just because 1970 is the "benchmark" to which they are both being compared?

B in both cases
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