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A set X; {a1, a2, a3, a4, a5} with non-zero elements have

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by AAPL » Fri Jun 01, 2018 4:49 am
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A set X: {a1, a2, a3, a4, a5} with non-zero elements have mean M. What is the mean of the set Y: {a1-1, a2-2, a3-3, a4+5, a5+1}?

A. M-3
B. M-2
C. M-1
D. M
E. M+1

The OA is D.

Set X:
Mean=M= (a1+a2+a3+a4+a5)/5
Sum of these values= 5M.

Set Y:
We see similar elements a1, a2, ...........
Combine them together and we know that their sum is equal to 5M.

Therefore
5M-1-2-3+5+1
=5M+0
=5M

The mean of set Y= 5M/5=M.

Mean of set X=Mean of set Y.

Has anyone another strategic approach to solve this PS question? Regards!
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by GMATGuruNY » Fri Jun 01, 2018 5:12 am
AAPL wrote:A set X: {a1, a2, a3, a4, a5} with non-zero elements have mean M. What is the mean of the set Y: {a1-1, a2-2, a3-3, a4+5, a5+1}?

A. M-3
B. M-2
C. M-1
D. M
E. M+1
Let Set X = {1, 2, 3, 4, 5}
Since the set is evenly spaced, the average is equal to the median:
M = 3.

Since Set Y = {A�-1, A₂-2, aA₃-3, A₄+5, A₅+1}, we get:
Set Y = (0, 0, 0, 9, 6}.
Mean of Set Y = (0+0+0+9+6)/5 = 3.

As illustrated by the values in blue, the mean of Set Y = M.

The correct answer is D.
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by Jeff@TargetTestPrep » Sun Jun 03, 2018 5:30 pm
AAPL wrote:A set X: {a1, a2, a3, a4, a5} with non-zero elements have mean M. What is the mean of the set Y: {a1-1, a2-2, a3-3, a4+5, a5+1}?

A. M-3
B. M-2
C. M-1
D. M
E. M+1
Since the mean of set X is M, (a1 + a2 + a3 + a4 + a5)/5 = M.

The mean of set Y is (a1-1 + a2-2 + a3-3 + a4+5 + a5+1)/5 = (a1 + a2 + a3 + a4 + a5)/5 = M.

Answer: D

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