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Is the average (arithmetic mean) of a, b, and c greater than 12?

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Is the average (arithmetic mean) of a, b, and c greater than 12?  [#permalink]

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New post 03 May 2017, 04:43
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Is the average (arithmetic mean) of a, b, and c greater than 12?

(1) The average (arithmetic mean) of a + 2, b − 7, and c + 6 is 10.
(2) a, b, and c are integers.

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Re: Is the average (arithmetic mean) of a, b, and c greater than 12?  [#permalink]

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New post 03 May 2017, 05:44
the question asks for (a + b + c)/3 > 12 ???
implies a + b + c >36

stat 1: (a+2 + b-7 + c+ 6) = 30
a+b+c = 29,,suff

stat 2 : no useful info.,,

ans A
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Re: Is the average (arithmetic mean) of a, b, and c greater than 12?  [#permalink]

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New post 03 May 2017, 06:11
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Bunuel wrote:
Is the average (arithmetic mean) of a, b, and c greater than 12?

(1) The average (arithmetic mean) of a + 2, b − 7, and c + 6 is 10.
(2) a, b, and c are integers.


Target question: Is the average (arithmetic mean) of a, b, and c greater than 12?

Statement 1: The average (arithmetic mean) of a + 2, b − 7, and c + 6 is 10
In other words, [(a + 2) + (b − 7) + (c + 6)]/3 = 10
Multiply both sides by 3 to get: (a + 2) + (b − 7) + (c + 6) = 30
Simplify to get: a + b + c = 29
The average of a, b and c = (a + b + c)/3 = 29/3
So, the average (arithmetic mean) of a, b, and c is NOT greater than 12
Since we can answer the target question with certainty, statement 1 is SUFFICIENT

Statement 2: a, b, and c are integers.
If it's not obvious that this information is not sufficient, consider the following two cases:
Case a: a = 100, b = 100 and c = 100, in which case the average of a, b and c IS greater than 12
Case b: a = 1, b = 1 and c = 1, in which case the average of a, b and c is NOT greater than 12
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

Answer:

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Re: Is the average (arithmetic mean) of a, b, and c greater than 12?  [#permalink]

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New post 06 May 2017, 10:44
from 1) a+b+c=29
So (a+b+c)/3=29/3<12 So suff

2) Insuff: no info is given about the values.


Ans is : A
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Re: Is the average (arithmetic mean) of a, b, and c greater than 12? &nbs [#permalink] 06 May 2017, 10:44
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