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The average of x1, x2, x3, x4, x5 is m.

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The average of x1, x2, x3, x4, x5 is m.

by Max@Math Revolution » Mon Apr 13, 2020 1:01 am
[GMAT math practice question]

The average of x1, x2, x3, x4, x5 is m. What is the average of x1-a, x2-2a, x3-3a, x4-4a, x5-5a?

A. m
B. m - 1/2a
C. m - a
D. m - 3a
E. m - 3/2a
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Re: The average of x1, x2, x3, x4, x5 is m.

by Max@Math Revolution » Wed Apr 15, 2020 8:53 pm
=>

Since m is the average of x1, x2, x3, x4, x5, we have m = (x1 + x2 + x3 + x4 + x5) / 5 or x1 + x2 + x3 + x4 + x5 = 5m.
Then the average of x1-a, x2-2a, x3-3a, x4-4a, x5-5a is
[(x1 - a) + (x2 - 2a) + (x3 - 3a) + (x4 - 4a) + (x5 - 5a)] / 5
= (x1 + x2 + x3 + x4 + x5 - 15a) / 5
= (x1 + x2 + x3 + x4 + x5 ) / 5 – 3a
= m – 3a

Therefore, D is the answer.
Answer: D
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