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Horace family

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Capthan
 Post subject: Horace family
 Post Posted: Mon Aug 18, 2008 7:31 am 
To install cable television in home, a certain company charges a basic fee of $30 plus a fee of $20 for each cable outlet installed in the home. How much did the cable company charges the Horace family for installing cable television in their home?

(1) The cable company installed three cable outlets in the Horace family home.

(2) The amount that the cable company charged the Horace family for installing cable television in their home was equivalent to an average(mean) charge of $30 per cable outlet installed.

Please explain why the answer is D?
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Ginc
 Post subject: Horace
 Post Posted: Mon Aug 18, 2008 8:20 am 
Option a) is sufficient as you are told directly how many sockets he installed

Optiob B) is sufficient because using average formula = s/n you can calculate how many plugs he installed
first you make x the unknown number of plugs.. the you calculate the sum as 20x +30/ x=30
cross multiply this will give you 20x +30 =30x-20
30= 30x-10x
30/10=x
3=x
therfore both stems are sufficient..
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RonPurewal
 Post subject: Re: Horace
 Post Posted: Mon Aug 25, 2008 6:02 am 
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ManhattanGMAT Staff


Posts: 7146
Ginc wrote:
Option a) is sufficient as you are told directly how many sockets he installed

Optiob B) is sufficient because using average formula = s/n you can calculate how many plugs he installed
first you make x the unknown number of plugs.. the you calculate the sum as 20x +30/ x=30
cross multiply this will give you 20x +30 =30x-20
30= 30x-10x
30/10=x
3=x
therfore both stems are sufficient..


yes.

notice that, because this is data sufficiency, there's actually no need to solve the equation in the second part.

just set it up:

Sum = Average x Number. so if "x" is the number of sockets installed, then Sum (total cost) = 30x.
but we also know that Sum = 30 + 20x.
therefore, 30x = 30 + 20x
sufficient
no reason to actually solve.
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