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The average of a set of 5 numbers is 20. If 4 additional numbers are a

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Bunuel
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The average of a set of 5 numbers is 20. If 4 additional numbers are a [#permalink] New post   11 Apr 2018, 21:29
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The average of a set of 5 numbers is 20. If 4 additional numbers are added to the set, the average increases to 24. What is the average of the additional 4 numbers?

A. 22
B. 25
C. 26
D. 28
E. 29
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Re: The average of a set of 5 numbers is 20. If 4 additional numbers are a [#permalink] New post   12 Apr 2018, 00:16
Bunuel wrote:
The average of a set of 5 numbers is 20. If 4 additional numbers are added to the set, the average increases to 24. What is the average of the additional 4 numbers?

A. 22
B. 25
C. 26
D. 28
E. 29


sum of 5 no.=5x20=100
sum of 9 no.= 9x24=216
difference =216-100=116
116 is basically the total of 4 no.

average=116/4
=29
thus, the correct answer is E.
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Re: The average of a set of 5 numbers is 20. If 4 additional numbers are a [#permalink] New post   12 Apr 2018, 00:22
Sum of 4 additional numbers = (24*9) - (20*5) = 116.
Hence their average = 116/4 = 29. Hence option E should be the answer.
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The average of a set of 5 numbers is 20. If 4 additional numbers are a [#permalink] New post   12 Apr 2018, 06:17
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Bunuel wrote:
The average of a set of 5 numbers is 20. If 4 additional numbers are added to the set, the average increases to 24. What is the average of the additional 4 numbers?

A. 22
B. 25
C. 26
D. 28
E. 29

\(A * n = S\)

The average of 5 numbers is 20
\((20 * 5) = 100 = Sum_1\)

4 numbers are added. Average increases to 24
\(n = (5 + 4) = 9\)
\((24 * 9) = 216 = Sum_2\)

\((Sum_2 - Sum_1) = Sum_3\) of the 4 extra numbers
\((216 - 100) = 116 = Sum_3\)
\(A = \frac{S}{n}\)
\(A = \frac{116}{4} = 29\)

Answer E
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Re: The average of a set of 5 numbers is 20. If 4 additional numbers are a [#permalink] New post   16 Apr 2018, 16:19
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Bunuel wrote:
The average of a set of 5 numbers is 20. If 4 additional numbers are added to the set, the average increases to 24. What is the average of the additional 4 numbers?

A. 22
B. 25
C. 26
D. 28
E. 29


Using the average formula: average = sum/number, we know the initial sum is 5 x 20 = 100. We can let x = the sum of the additional 4 numbers and create the equation:

(100 + x)/(5 + 4) = 24

(100 + x)/9 = 24

100 + x = 216

x = 116

The average of the 4 numbers is 116/4 = 29.

Answer: E
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Re: The average of a set of 5 numbers is 20. If 4 additional numbers are a [#permalink]
16 Apr 2018, 16:19
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