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Re: Gasoline and Electricity [#permalink]
krazo wrote:
Here is one I thought was pretty good...

A polling company found that, of 300 households surveyed, 120 spent at least $100 per month on both gasoline and electricity, 60 spent at least $100 per month on gasoline but not on electricity, and for every household that did not spend at least $100 per month on gasoline or electricity, 4 spent at least $100 per month on electricity but not on gasoline. How many of the 300 households did not spend at least $100 per month on either gasoline or electricity?

(A) 24
(B) 30
(C) 36
(D) 90
(E) 96


120 spend $100 on gas & electricity
60 spend $100 on gas but not on electricity
For every one that spent <$100 on both there are 4 that spent $100 on electricity not gas

Let the ones that spent on neither be x
The ones that spent on just electricity will be 4x

Total households = Those who spend >$100 on both + Those who spend >$100 on just one + Those who spend <$100 on both = 120 + 60 + 4x + x

300 = 180 + 5x implies x=24

Answer is (A)
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Re: A polling company found that, of 300 households surveyed [#permalink]
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A polling company found that, of 300 households surveyed, 120 spent at least $100 per month on both gasoline and electricity, 60 spent at least $100 per month on gasoline but not on electricity, and for every household that did not spend at least $100 per month on gasoline or electricity, 4 spent at least $100 per month on electricity but not on gasoline. How many of the 300 households did not spend at least $100 per month on either gasoline or electricity?

A. 24
B. 30
C. 36
D. 90
E. 96

{Total} = {Only Gasoline} + {Only Electricity} + {Both} + {Neither}. Notice that this formula is different from {Total} = {Group #1} + {Group #2}} - {Both} + {Neither};

\(300 = 60 + 4x + 120 + x\) --> \(x=24\).

Answer: A.

Hope it's clear.
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Re: A polling company found that, of 300 households surveyed [#permalink]
Bunuel wrote:
A polling company found that, of 300 households surveyed, 120 spent at least $100 per month on both gasoline and electricity, 60 spent at least $100 per month on gasoline but not on electricity, and for every household that did not spend at least $100 per month on gasoline or electricity, 4 spent at least $100 per month on electricity but not on gasoline. How many of the 300 households did not spend at least $100 per month on either gasoline or electricity?

A. 24
B. 30
C. 36
D. 90
E. 96

{Total} = {Only Gasoline} + {Only Electricity} + {Both} + {Neither}. Notice that this formula is different from {Total} = {Group #1} + {Group #2}} - {Both} + {Neither};

\(300 = 60 + 4x + 120 + x\) --> \(x=24\).

Answer: A.

Hope it's clear.

I know this is very basic , but a reconfirmation will help

" My confusion was the term " OR "

A OR B means AUB ( Total ) right so in this case E OR G means EUG( Total )

so EUG = only E + Only G + Both + Neither ( This one we are using )
also EUG = Group E + group G - both + Neither ( This one we are not using here )


Please let me now if anything that I have written in Blue is wrong !!

I want to understand if A or B = AUB = Total ??
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Re: A polling company found that, of 300 households surveyed [#permalink]
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stne wrote:
Bunuel wrote:
A polling company found that, of 300 households surveyed, 120 spent at least $100 per month on both gasoline and electricity, 60 spent at least $100 per month on gasoline but not on electricity, and for every household that did not spend at least $100 per month on gasoline or electricity, 4 spent at least $100 per month on electricity but not on gasoline. How many of the 300 households did not spend at least $100 per month on either gasoline or electricity?

A. 24
B. 30
C. 36
D. 90
E. 96

{Total} = {Only Gasoline} + {Only Electricity} + {Both} + {Neither}. Notice that this formula is different from {Total} = {Group #1} + {Group #2}} - {Both} + {Neither};

\(300 = 60 + 4x + 120 + x\) --> \(x=24\).

Answer: A.

Hope it's clear.

I know this is very basic , but a reconfirmation will help

" My confusion was the term " OR "

A OR B means AUB ( Total ) right so in this case E OR G means EUG( Total )

so EUG = only E + Only G + Both + Neither ( This one we are using )
also EUG = Group E + group G - both + Neither ( This one we are not using here )


Please let me now if anything that I have written in Blue is wrong !!

I want to understand if A or B = AUB = Total ??


Two formulas are:
{Total} = {Group #1} + {Group #2} - {Both} + {Neither}
{Total} = {Only Group #1} + {Only Group #2} + {Both} + {Neither}

Now, if we are told that there are 10 people in {Group #1} and 15 people in {Group #2}, then the number of people in {Group #1} OR in {Group #2} can be expressed as {Group #1} + {Group #2} - {Both}. But to get the total number of people you should add to that the number of people who are in neither of groups.

Hope it's clear.
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Re: A polling company found that, of 300 households surveyed [#permalink]
Bunuel wrote:
A polling company found that, of 300 households surveyed, 120 spent at least $100 per month on both gasoline and electricity, 60 spent at least $100 per month on gasoline but not on electricity, and for every household that did not spend at least $100 per month on gasoline or electricity, 4 spent at least $100 per month on electricity but not on gasoline. How many of the 300 households did not spend at least $100 per month on either gasoline or electricity?

A. 24
B. 30
C. 36
D. 90
E. 96

{Total} = {Only Gasoline} + {Only Electricity} + {Both} + {Neither}. Notice that this formula is different from {Total} = {Group #1} + {Group #2}} - {Both} + {Neither};

\(300 = 60 + 4x + 120 + x\) --> \(x=24\).

Answer: A.

Hope it's clear.


HI Bunuel,

I know its a silly question but i didn't understand how you took 4x from question stem.

Please clarify.

Thanks.
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A polling company found that, of 300 households surveyed [#permalink]
PathFinder007 wrote:
Bunuel wrote:
A polling company found that, of 300 households surveyed, 120 spent at least $100 per month on both gasoline and electricity, 60 spent at least $100 per month on gasoline but not on electricity, and for every household that did not spend at least $100 per month on gasoline or electricity, 4 spent at least $100 per month on electricity but not on gasoline. How many of the 300 households did not spend at least $100 per month on either gasoline or electricity?

A. 24
B. 30
C. 36
D. 90
E. 96

{Total} = {Only Gasoline} + {Only Electricity} + {Both} + {Neither}. Notice that this formula is different from {Total} = {Group #1} + {Group #2}} - {Both} + {Neither};

\(300 = 60 + 4x + 120 + x\) --> \(x=24\).

Answer: A.

Hope it's clear.


HI Bunuel,

I know its a silly question but i didn't understand how you took 4x from question stem.

Please clarify.

Thanks.


Not Bunuel, but lets try :)

The answer lies in the highlighted part of the question

Only Electricity is 4 times of (No Gas No electricity)

So, if "x" = No Gas No electricity, then 4x = Only electricity

Please refer the Venn diagram above; it explains perfect

In this problem, the term "atleast 100" is the confusion creator which is repeated 5 times; although "100" is not required for any calculation.

May be GMAT trick :)
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Re: A polling company found that, of 300 households surveyed [#permalink]
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krazo wrote:
A polling company found that, of 300 households surveyed, 120 spent at least $100 per month on both gasoline and electricity, 60 spent at least $100 per month on gasoline but not on electricity, and for every household that did not spend at least $100 per month on gasoline or electricity, 4 spent at least $100 per month on electricity but not on gasoline. How many of the 300 households did not spend at least $100 per month on either gasoline or electricity?

A. 24
B. 30
C. 36
D. 90
E. 96


We can create the following equation:

Total = number who spent at least 100 on gasoline only + number who spent at least 100 on electricity only + number who spend at least 100 on both + number who spent at least 100 on neither

If we let x = number who spent at least 100 on neither, then 4x = number who spent at least 100 on electricity only, and we have:

300 = 60 + 4x + 120 + x

300 = 180 + 5x

120 = 5x

x = 24

Answer: A
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Re: A polling company found that, of 300 households surveyed [#permalink]
krazo wrote:
A polling company found that, of 300 households surveyed, 120 spent at least $100 per month on both gasoline and electricity, 60 spent at least $100 per month on gasoline but not on electricity, and for every household that did not spend at least $100 per month on gasoline or electricity, 4 spent at least $100 per month on electricity but not on gasoline. How many of the 300 households did not spend at least $100 per month on either gasoline or electricity?

A. 24
B. 30
C. 36
D. 90
E. 96



a ratio between "none and only electricity" is given

so, none and only electricity = (300 - 120 -60) = 120

now, according to the ratio
120 * 1/5 = 24

thanks
:cool:
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Re: A polling company found that, of 300 households surveyed [#permalink]
krazo wrote:
A polling company found that, of 300 households surveyed, 120 spent at least $100 per month on both gasoline and electricity, 60 spent at least $100 per month on gasoline but not on electricity, and for every household that did not spend at least $100 per month on gasoline or electricity, 4 spent at least $100 per month on electricity but not on gasoline. How many of the 300 households did not spend at least $100 per month on either gasoline or electricity?

A. 24
B. 30
C. 36
D. 90
E. 96


CAN BE SOLVED USING 2X2 MATRIX

---- -----100$ ELECT-----N 100$ ELEC------TOTAL
100$ GAS---120-----------60---------------180
N100$GAS---4X------------X----------120
TOTAL ---120+4X----------60+5X------300
SO 4X+X=120
X=24 IMO A
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Re: A polling company found that, of 300 households surveyed [#permalink]
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Re: A polling company found that, of 300 households surveyed [#permalink]
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