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For a certain set of 3 numbers, is the average(arithmetic mean) equal  [#permalink]

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For a certain set of 3 numbers, is the average(arithmetic mean) equal to the median?

(1) The range of the set is double the difference between the smallest number in the set and the middle number.

(2) The set consist of three numbers 10, 16 and 22.

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Re: For a certain set of 3 numbers, is the average(arithmetic mean) equal  [#permalink]

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tirupatibalaji wrote:
(Q) For a certain set of 3 numbers, is the average(arithmetic mean) equal to the median?

(1) The range of the set is double the difference between the smallest number in the set and the middle number.

(2) The set consist of three numbers 10, 16 and 22.

For a certain set of 3 numbers, is the average (arithmetic mean) equal to the median?

Assume the numbers in ascending order are: a, b, and c.

The range of a set is the difference between the largest and smallest numbers of a set: Range=Largest-Smallest=c-a
The median of a set with odd # of elements is the middle number (when arranged in ascending or descending order): median=b.

Question: is (a+b+c)/3=b --> is a+c=2b?

(1) The range of the set is double the difference between the smallest number in the set and the middle number --> c-a=2(b-a) --> c+a=2b. Sufficient.

(2) The set consist of three numbers 10, 16 and 22 --> directly gives the numbers of the set so we can get the average as well as the median. Sufficient.

Answer: D.
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Re: For a certain set of 3 numbers, is the average(arithmetic mean) equal  [#permalink]

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1
For a certain set of 3 numbers, is the average (arithmetic mean) equal to the median?

(1) The range of the set is double the difference between the smallest number in the set and the middle number.
(2) The set consists of the three numbers 10, 16, and 22.
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Re: For a certain set of 3 numbers, is the average(arithmetic mean) equal  [#permalink]

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1
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enigma123 wrote:
For a certain set of 3 numbers, is the average (arithmetic mean) equal to the median?
(1) The range of the set is double the difference between the smallest number in the set and the middle number.
(2) The set consists of the three numbers 10, 16, and 22.

I understand B is sufficient. How can A be sufficient? Any thoughts please?

For a certain set of 3 numbers, is the average (arithmetic mean) equal to the median?

Let the 3 numbers in ascending order be: a, b, and c.

The range of a set is the difference between the largest and the smallest numbers of a set, so Range=Largest-Smallest=c-a;
The median of a set with odd # of numbers is the middle number (when arranged in ascending or descending order):, so median=b.

Question: is (a+b+c)/3=b --> is a+c=2b?

(1) The range of the set is double the difference between the smallest number in the set and the middle number --> c-a=2(b-a) --> c+a=2b. Sufficient.

(2) The set consist of three numbers 10, 16 and 22 --> directly gives the numbers of the set so we can get the average as well as the median. Sufficient.

Answer: D.

Hope it's clear.
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Re: For a certain set of 3 numbers, is the average(arithmetic mean) equal  [#permalink]

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dcsushant wrote:
For a certain set of 3 numbers, is the average (arithmetic mean) equal to the median?
(1) The range of the set is double the difference between the smallest number in the set and the middle number.
(2) The set consists of the three numbers 10, 16, and 22.

let three numbers be x,y,z. Also we know that for an evenly spaced numbers mean= median.

suppose x,y,z are evenly spaced i.e. differene between first and second, and second and third is same. thus we have
y-x=z-y
or 2y=x+z---------------------1)

let's consider st.1:
z-x=2(y-x)
z-x=2y-2x
2y=z+x
as can be seen from 1, thus these numbers are evenly spaced. hence mean=median. therefore statement 1 alone is sufficient.

st.2 again clearly sufficient. as value of x,y,z are given to us.

hence answer should be D
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GMAT 1: 800 Q51 V49 GRE 1: Q170 V170 Re: For a certain set of 3 numbers, is the average(arithmetic mean) equal  [#permalink]

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Hi All,

For anyone interested - a slightly tougher variation of this question appears in the new OG2016 (DS #135) - it's one of the *new* questions and it showcases the same logic.

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For a certain set of 3 numbers, is the average(arithmetic mean) equal  [#permalink]

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tirupatibalaji wrote:
For a certain set of 3 numbers, is the average(arithmetic mean) equal to the median?

(1) The range of the set is double the difference between the smallest number in the set and the middle number.

(2) The set consist of three numbers 10, 16 and 22.

Say three numbers are X, Y , z in increasing order. Median = Y, hence range =Z-X ------equation(1)

take statement1: range =2(Y-X)----------equation(2)
From equation(1) and equation(2)

2(Y-X)= Z-X .... 2Y-2X=Z-X this gives Z=2Y-X ----------equation(3)
average = $$\frac{(X+Y+Z)}{3}$$ .... put the value from equation 3
average = Y = Median

Hence sufficient
take statement2: median =16
$$average = \frac{(10+16+22)}{3}$$ = $$\frac{48}{3}$$ =16
Hence sufficient

Ans: D
_________________ For a certain set of 3 numbers, is the average(arithmetic mean) equal   [#permalink] 25 Jul 2017, 00:40
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