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# The average (arithmetic mean) of five numbers is 3x + 4. If one of the

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The average (arithmetic mean) of five numbers is 3x + 4. If one of the  [#permalink]

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01 Apr 2015, 03:49
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The average (arithmetic mean) of five numbers is 3x + 4. If one of the numbers is 7x - 4, what is the average of the other four numbers?

A. 1.6x + 3.2
B. 1.6x + 4.8
C. 2x + 4
D. 2x + 6
E. 4x + 8

Kudos for a correct solution.

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Re: The average (arithmetic mean) of five numbers is 3x + 4. If one of the  [#permalink]

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01 Apr 2015, 03:54
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The answer is 2x + 6, which is not given in the answer choices
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Re: The average (arithmetic mean) of five numbers is 3x + 4. If one of the  [#permalink]

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01 Apr 2015, 03:55
TARGET730 wrote:
The answer is 2x + 6, which is not given in the answer choices

__________
Edited. Thank you.
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Re: The average (arithmetic mean) of five numbers is 3x + 4. If one of the  [#permalink]

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01 Apr 2015, 04:38
TARGET730 wrote:
The answer is 2x + 6, which is not given in the answer choices

im getting (2x+4)
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Re: The average (arithmetic mean) of five numbers is 3x + 4. If one of the  [#permalink]

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01 Apr 2015, 05:02
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7x-4 + y (all four numbers) / 5 = 3x+4

7x-4 +y = 15x+20

y = 8x+24

Avg. of 4 numbers = 2x+6.
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Re: The average (arithmetic mean) of five numbers is 3x + 4. If one of the  [#permalink]

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01 Apr 2015, 06:11
This is what I did;

5 numbers, average of 5 numbers = 3x+4
5*(3x+4) = 15x + 20
15x + 20 - 7x - 4= 8x + 16

8x + 16 / 4 = 2x + 4.

What did I do wrong?
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Re: The average (arithmetic mean) of five numbers is 3x + 4. If one of the  [#permalink]

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01 Apr 2015, 15:52
SavageBrother wrote:
This is what I did;

5 numbers, average of 5 numbers = 3x+4
5*(3x+4) = 15x + 20
15x + 20 - 7x - 4= 8x + 16

8x + 16 / 4 = 2x + 4.

What did I do wrong?

You forgot the minus buddy! 15x + 20 - (7x - 4)= 8x + 24 / 4 is the answer!
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Re: The average (arithmetic mean) of five numbers is 3x + 4. If one of the  [#permalink]

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01 Apr 2015, 23:16
Answer = D. 2x + 6

Let the addition of other 4 numbers = a; we require to find $$\frac{a}{4}$$

$$\frac{a + 7x-4}{5} = 3x+4$$

a = 8x+24

$$\frac{a}{4} = 2x+6$$
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Re: The average (arithmetic mean) of five numbers is 3x + 4. If one of the  [#permalink]

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02 Apr 2015, 02:13
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Bunuel wrote:
The average (arithmetic mean) of five numbers is 3x + 4. If one of the numbers is 7x - 4, what is the average of the other four numbers?

A. 1.6x + 3.2
B. 1.6x + 4.8
C. 2x + 4
D. 2x + 6
E. 4x + 8

Kudos for a correct solution.

Sum(5 nos)/5 = 3x + 4
Sum(7x-4 + 4 nos) = 15x + 20
Sum( 4 nos) = 8x + 24
AM(4 nos) = 2x + 6

Option D
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Re: The average (arithmetic mean) of five numbers is 3x + 4. If one of the  [#permalink]

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02 Apr 2015, 02:13
1
Bunuel wrote:
The average (arithmetic mean) of five numbers is 3x + 4. If one of the numbers is 7x - 4, what is the average of the other four numbers?

A. 1.6x + 3.2
B. 1.6x + 4.8
C. 2x + 4
D. 2x + 6
E. 4x + 8

Kudos for a correct solution.

Sum(5 nos)/5 = 3x + 4
Sum(7x-4 + 4 nos) = 15x + 20
Sum( 4 nos) = 8x + 24
AM(4 nos) = 2x + 6

Option D
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Joined: 02 Sep 2009
Posts: 60480
Re: The average (arithmetic mean) of five numbers is 3x + 4. If one of the  [#permalink]

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06 Apr 2015, 05:57
1
Bunuel wrote:
The average (arithmetic mean) of five numbers is 3x + 4. If one of the numbers is 7x - 4, what is the average of the other four numbers?

A. 1.6x + 3.2
B. 1.6x + 4.8
C. 2x + 4
D. 2x + 6
E. 4x + 8

Kudos for a correct solution.

MAGOOSH OFFICIAL SOLUTION:
Attachment:

averageis3xplus4_text.PNG [ 18.42 KiB | Viewed 3738 times ]

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Re: The average (arithmetic mean) of five numbers is 3x + 4. If one of the  [#permalink]

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10 Dec 2016, 08:32
Here is my solution to this one -->
Sum(5)=> 15x+20
Sum(4)=> 15x+20-(7x-4) => 8x+24
Hence Mean of 4 numbers -> 2x+6

Hence D
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Re: The average (arithmetic mean) of five numbers is 3x + 4. If one of the  [#permalink]

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25 Nov 2019, 20:30

Solution

Given
• The average (arithmetic mean) of five numbers is 3x + 4
• one of the numbers is 7x – 4.

To find
• The average of the other four numbers.

Approach and Working out

• Average of 5 numbers = 3x +4
o Sum of numbers / 5 = 3x+4
• One of the numbers = 7x-4
o 7x -4 + sum of remaining 4 numbers / 5 = 3x + 4
o 7x -4 + sum of remaining 4 numbers = 15x + 20
o Sum of remaining 4 numbers = 8x + 24
• Average of remaining 4 numbers = 8x +24 /4 = 2x +6
Thus, option D is the correct answer.
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The average (arithmetic mean) of five numbers is 3x + 4. If one of the  [#permalink]

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15 Dec 2019, 15:42
The total of the five numbers is $$5*(3x+4)=15x+20$$
One of the numbers is $$7x-4$$. Therefore, $$15x+20=(7x-4)+a+b+c+d$$
and $$8x+24=a+b+c+d$$
So the average of the other four numbers (a, b, c, d) is $$\frac{(8x+24)}{4}=2x+6$$ (Answer D)
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The average (arithmetic mean) of five numbers is 3x + 4. If one of the   [#permalink] 15 Dec 2019, 15:42
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