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# The average (arithmetic mean) of 8 numbers is Z, and one of the number

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The average (arithmetic mean) of 8 numbers is Z, and one of the number  [#permalink]

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31 Oct 2016, 03:11
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5% (low)

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86% (01:21) correct 14% (01:05) wrong based on 83 sessions

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The average (arithmetic mean) of 8 numbers is Z, and one of the numbers is 14. If 14 is replaced with 28, then what is the new average (arithmetic mean) in terms of Z?

A. Z + 1/2
B. Z + 7/4
C. Z + 2
D. Z + 4
E. 2Z + 1

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Re: The average (arithmetic mean) of 8 numbers is Z, and one of the number  [#permalink]

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31 Oct 2016, 03:48
1
Let sum of 7 numbers be S
$$\frac{S+14}{8}= Z$$
When 14 is replaced by 28,
new average = S+28/8
=$$\frac{(S+14+14)}{8}$$

=$$Z +\frac{14}{8}$$
= $$Z + \frac{7}{4}$$
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Re: The average (arithmetic mean) of 8 numbers is Z, and one of the number  [#permalink]

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31 Oct 2016, 08:13
Bunuel wrote:
The average (arithmetic mean) of 8 numbers is Z, and one of the numbers is 14. If 14 is replaced with 28, then what is the new average (arithmetic mean) in terms of Z?

A. Z + 1/2
B. Z + 7/4
C. Z + 2
D. Z + 4
E. 2Z + 1

$$\frac{(8z - 14 + 28)}{8}$$

Or, $$\frac{(8z + 14)}{8}$$

Or, $$\frac{(4z + 7)}{4}$$

Or, $$z + \frac{7}{4}$$

So, correct answer will be (B) $$z + \frac{7}{4}$$
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Re: The average (arithmetic mean) of 8 numbers is Z, and one of the number  [#permalink]

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09 Dec 2016, 02:28
Here is my solution -->
Sum(8)=8*z
Replacing 14 by 28
New sum=8z-14+28=8z+14
Hence New Mean = $$\frac{8z+14}{8} = z+\frac{7}{4}$$

Hence B

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Re: The average (arithmetic mean) of 8 numbers is Z, and one of the number  [#permalink]

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05 Oct 2018, 08:44
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Re: The average (arithmetic mean) of 8 numbers is Z, and one of the number &nbs [#permalink] 05 Oct 2018, 08:44
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