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

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Math Expert
Joined: 02 Sep 2009
Posts: 44566
The average of a set of 5 numbers is 20. If 4 additional numbers are a [#permalink]

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11 Apr 2018, 21:29
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100% (01:01) correct 0% (00:00) wrong based on 12 sessions

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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
[Reveal] Spoiler: OA

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Manager
Joined: 31 Oct 2013
Posts: 96
Concentration: Accounting, Finance
GPA: 3.68
WE: Analyst (Accounting)
Re: The average of a set of 5 numbers is 20. If 4 additional numbers are a [#permalink]

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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.
Intern
Joined: 04 Apr 2018
Posts: 22
Re: The average of a set of 5 numbers is 20. If 4 additional numbers are a [#permalink]

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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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Joined: 22 May 2016
Posts: 1539
The average of a set of 5 numbers is 20. If 4 additional numbers are a [#permalink]

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12 Apr 2018, 06:17
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
$$(216 - 100) = 116 = Sum_3$$
$$A = \frac{S}{n}$$
$$A = \frac{116}{4} = 29$$

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Re: The average of a set of 5 numbers is 20. If 4 additional numbers are a [#permalink]

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16 Apr 2018, 16:19
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.

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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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