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Re: The average (arithmetic mean) of five numbers is 3x + 4. If one of the [#permalink]
TARGET730 wrote:
The answer is 2x + 6, which is not given in the answer choices

can u please explain how you got 2x+6 as the answer.
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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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]
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]
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]
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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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


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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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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


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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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Expert Reply
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
averageis3xplus4_text.PNG [ 18.42 KiB | Viewed 9520 times ]
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Re: The average (arithmetic mean) of five numbers is 3x + 4. If one of the [#permalink]
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]
Expert Reply

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


Remember that average = sum / quantity. Since the average of the five numbers is 3x + 4, the sum of these five numbers is 5 * (3x + 4) = 15x + 20. We are told that one of the numbers is 7x - 4, thus the sum of the remaining four numbers is 15x + 20 - (7x - 4) = 15x + 20 - 7x + 4 = 8x + 24. Since the sum of the four numbers besides 7x - 4 is 8x + 24, the average of these four numbers is (8x + 24)/4 = 8x/4 + 24/4 = 2x + 6.

Answer: 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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