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puzzling DS Q from gmat prep

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puzzling DS Q from gmat prep

by harry_x1 » Sat Jun 23, 2007 1:22 am
1. Is the average of 5 different positive integers at least 30:

(1) Each integer is a multiple of 10
(2) sum of five integers is 160.

The gmat prep says that each statement alone is sufficient. But how its possible. Only statement 2 is sufficient alone , and not statemenr no 1. Please help
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Re: puzzling DS Q from gmat prep

by jayhawk2001 » Sat Jun 23, 2007 6:18 am
harry_x1 wrote:1. Is the average of 5 different positive integers at least 30:

(1) Each integer is a multiple of 10
(2) sum of five integers is 160.

The gmat prep says that each statement alone is sufficient. But how its possible. Only statement 2 is sufficient alone , and not statemenr no 1. Please help
Since the question asks for "atleast 30" - consider the first 5 positive
integers i.e. 10, 20, 30, 40 and 50. Average is 30. So, replacing any
number in the list with a greater number would mean an increase in
average. So, (1) is sufficient.

(2) is sufficient as well
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by jayhawk2001 » Sat Jun 23, 2007 9:59 am
Anonymous wrote:is zero not a multiple of 10 that will make the multiple as 0,10,20,30,40
Nope. It says "positive integer". You'll have to exclude 0
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by jrbrown2 » Sun Jun 24, 2007 9:10 am
Jayhawk's explanation for statement 1 is perfect.

For statement 2: the sum of the five numbers is 160.

Average is Sum of numbers divided by amount of numbers. So the avg is 160/5 = 32 which is at least 30.

D...each statement alone is sufficient
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by discreet » Thu Jun 28, 2007 12:09 am
Zero is neither negative nor positive.Also remember that IT IS AN EVEN INTEGER.
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by moneyman » Sun Jul 01, 2007 9:36 am
Statement (1) says that every number is a multiple of 10
So,even if we take the least values for example 10,20,20,20 and 20 we would get an average of 45.So (1) is sufficient.

Statement(2) itself gives the total so dividing the total by 5 gives us an answer.So (2) is sufficient as well.

Thus,the answer D
Maxx
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puzzled

by charlie » Wed Aug 01, 2007 8:38 pm
I am a bit puzzled.
According to (I) let the 5 integers be 10,10,10,10,10
In that case the average is 10 <30.
According to (I) we can have 10,20,30,40,50 as the numbers which give the average as 30.
If we put any multiple of 10 greater than 30 the average increases.
Hence, considering statement I we can have an average that is less than 30, equal to 30 & greater than 30.
WE cannot pinpoint. I believe A is insufficient.
PLease correct me if I am wrong.
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by paradox » Wed Aug 01, 2007 9:43 pm
Charlie, the question says they are 5 *different* integers.
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by charlie » Thu Aug 02, 2007 10:16 am
oops :(
Thanks Paradox. I need to shrug of these oversights.
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