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average

by cat er ina » Thu Apr 15, 2010 12:10 am
It's the second time that it shows up on my gmat prep test and still don't get this!!

If the average of the 4 numbers n+2, 2n-3, 4n+1 AND 7n+4 is 15 what is the value of n?

11/14, 4 , 32/7, 11, 13

the answer is 4

THANK YOU IN ADVANCE!!
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by gmatmachoman » Thu Apr 15, 2010 12:16 am
cat er ina wrote:It's the second time that it shows up on my gmat prep test and still don't get this!!

If the average of the 4 numbers n+2, 2n-3, 4n+1 AND 7n+4 is 15 what is the value of n?

11/14, 4 , 32/7, 11, 13

the answer is 4

THANK YOU IN ADVANCE!!

Hey there...

There is a pretty much nice formula for devising averages!!

Average : Sum on N numbers/(N)

15 = ( n+2 + 2n-3 + 4n+1 + 7n+4)/(4)
15 * 4= 14n +4

60 -4 = 14 n

n = 56/14
=4

Hope this helps.
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by neerajkumar1_1 » Thu Apr 15, 2010 12:19 am
the mean(or avg)=sum/total

hence (n+2+2n-3+4n+1+7n+4)/4=15

=> 14n + 4 = 60
=> 14n = 56
=> n = 4
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by cat er ina » Thu Apr 15, 2010 12:34 am
neerajkumar1_1 wrote:the mean(or avg)=sum/total

hence (n+2+2n-3+4n+1+7n+4)/4=15

=> 14n + 4 = 60
=> 14n = 56
=> n = 4

TRUEEE How silly I used to set everything equal15 which is not the product of the set but the average!
thank you guys you are a salvation!
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