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If the average(arithmetic mean) of four different numbers is

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DS question [#permalink] New post 07 Sep 2010, 13:22
If the average (arithmetic mean) of four different numbers is 30, how many of the numbers are greater than 30?

1) None of the four numbers is greater than 60
2) Two of the four numbers are 9 and 10 respectively
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Re: DS question [#permalink] New post 07 Sep 2010, 13:57
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aiming4mba wrote:
If the average (arithmetic mean) of four different numbers is 30, how many of the numbers are greater than 30?

(1) None of the four numbers is greater than 60
(2) Two of the four numbers are 9 and 10 respectively


If the average (arithmetic mean) of four different numbers is 30, how many of the numbers are greater than 30?

a+b+c+d=4*30=120

(1) None of the four numbers is greater than 60. Many combinations are possible. For example, numbers can be: 20-25-30-45 (only one number is greater than 30) OR 15-20-40-45 (two number are greater than 30). Not sufficient.

(2) Two of the four numbers are 9 and 10 respectively. Also not sufficient, consider: 0-9-10-101 OR 9-10-35-66. Not sufficient.

(1)+(2) As two of the four numbers are 9 and 10 then the sum of other two must be 120-(9+10)=101. Now, as the greatest number can be at most 60, then the least value of the other one is 41, so in any case two numbers will be more than 30. Sufficient.

Answer: C.
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Re: GMAT Prep DS: Average of four different numbers is 30 [#permalink] New post 18 Oct 2011, 10:09
Thanks Brunel :)
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If the average arthimetic mean of four different numbers is [#permalink] New post 25 Oct 2011, 23:14
If the average arthimetic mean of four different numbers is 30, how many of the numbers are greater than 30?

1. None of the four numbers is greater than 60?

2. Two of the four numbers are 9 and 10 respectively.

can anyone explain
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Re: Statistics [#permalink] New post 26 Oct 2011, 02:58
Statement 1
Not sufficient

We have max no as 60
so the NOs that can be more than 30 can be 1 or 2 or 3

Statement 2 not sufficient
we have two numbers as 9 and 10 but in the other two numbers one one or both can be more than two

both statements together
sum of known two numbers is 18 so sum of other two numbers must be 101
If no number is more than 60 then both should be more than 30


ans C

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Re: Statistics [#permalink] New post 26 Oct 2011, 02:58
Statement 1
Not sufficient

We have max no as 60
so the NOs that can be more than 30 can be 1 or 2 or 3

Statement 2 not sufficient
we have two numbers as 9 and 10 but in the other two numbers one one or both can be more than two

both statements together
sum of known two numbers is 18 so sum of other two numbers must be 101
If no number is more than 60 then both should be more than 30


ans C

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Re: Statistics [#permalink] New post 26 Oct 2011, 04:54
Guys Thanks for the explanation :)
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Re: Statistics   [#permalink] 26 Oct 2011, 04:54
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