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The average (arithmetic mean) of seven numbers is 12.2

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The average (arithmetic mean) of seven numbers is 12.2 [#permalink] New post   28 Apr 2015, 20:36
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The average (arithmetic mean) of seven numbers is 12.2
If the sum of four of these numbers is 42.8, what is the average of the other 3 numbers?
(a) 12.4
(b) 14.2
(c) 16.8
(d) 18.6
(e) 19.2
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B
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Re: The average (arithmetic mean) of seven numbers is 12.2 [#permalink] New post   28 Apr 2015, 21:02
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Hi dkumar2012,

This question is based completely on 'Average Formula' rules. If you're comfortable with the math involved, then you'll likely find it easiest to take an Algebraic approach to solving it.

We're told that the average of 7 numbers is 12.2

(Sum of numbers)/7 = 12.2

Sum of numbers = (12.2)(7) = 85.4

Next, we're told that the sum of 4 (of the 7) numbers is 42.8

From this information, we can calculate the sum of the OTHER 3 numbers:

85.4 - 42.8 = 42.6

The question asks for the AVERAGE of the OTHER 3 numbers....

42.6/3 = 14.2

Final Answer:
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B


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Re: The average (arithmetic mean) of seven numbers is 12.2 [#permalink] New post   29 Apr 2015, 03:36
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dkumar2012 wrote:
The average (arithmetic mean) of seven numbers is 12.2
If the sum of four of these numbers is 42.8, what is the average of the other 3 numbers?
(a) 12.4
(b) 14.2
(c) 16.8
(d) 18.6
(e) 19.2


As we have quite big intervals in answers we can speed solving by rounding numbers.
First of all sum of our seven numbers will be equal \(average * 7\)
\(12*7=84\) (a little more in reality)
now we should subtract sum of four numbers
\(84-42 = 42\) (a little less in reality so we equalize this two operations)
and now we should find average for three numbers by dividing their sum on \(3\)
\(42/3 = 14\)

And we see that closest answer is B
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Re: The average (arithmetic mean) of seven numbers is 12.2 [#permalink] New post   29 Apr 2015, 10:11
n=7, xhat=12.2, sum of 4 numbers = 42,8.

Total=n*xhat=85,4.
The three remaining: 85,4-42,8=42,6.

42,6/3=14,2 = B
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Re: The average (arithmetic mean) of seven numbers is 12.2 [#permalink] New post   16 Dec 2016, 17:40
Sum(7)=7*12.2
Sum(4)=42.8

Hence Sum(3)=42.6

Hence Mean = 14.2

Hence B
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Re: The average (arithmetic mean) of seven numbers is 12.2 [#permalink] New post   17 Dec 2016, 07:56
dkumar2012 wrote:
The average (arithmetic mean) of seven numbers is 12.2
If the sum of four of these numbers is 42.8, what is the average of the other 3 numbers?
(a) 12.4
(b) 14.2
(c) 16.8
(d) 18.6
(e) 19.2


Total of 7 numbers is 12.2*7 = 85.4

Total of 4 numbers is 42.8

So, Total of 3 numbers is 85.4 - 42.8 = 42.6

Average of the 3 numbers is 42.6/3 = 14.2

Hence, answer will be (B) 14.2
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Re: The average (arithmetic mean) of seven numbers is 12.2 [#permalink] New post   16 Oct 2018, 20:03
Easy way out

Total of 7 numbers = 85.4 (1)
Total of 4 numbers = 42.8 (2)
(1)-(2)
Total of 3 numbers = 42.60
Average of 3 numbers = 42.60/3 =14.20
Hence Option B
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Re: The average (arithmetic mean) of seven numbers is 12.2 [#permalink]
16 Oct 2018, 20:03
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