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# If the average (arithmetic mean) monthly sales of a department store

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Math Expert
Joined: 02 Sep 2009
Posts: 61371
If the average (arithmetic mean) monthly sales of a department store  [#permalink]

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11 Nov 2019, 02:43
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Difficulty:

65% (hard)

Question Stats:

41% (01:42) correct 59% (01:29) wrong based on 28 sessions

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If the average (arithmetic mean) monthly sales of a department store was y dollars during a certain period of several years, what is the average biannual sales over the same period?

(1) The period includes exactly 4 years.
(2) y = 500.

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Math Expert
Joined: 02 Aug 2009
Posts: 8248
Re: If the average (arithmetic mean) monthly sales of a department store  [#permalink]

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13 Nov 2019, 23:05
Bunuel wrote:
If the average (arithmetic mean) monthly sales of a department store was y dollars during a certain period of several years, what is the average biannual sales over the same period?

(1) The period includes exactly 4 years.
(2) y = 500.

Are You Up For the Challenge: 700 Level Questions

So average monthly sales is y, and biannual or 6-monthly average will be 6y..
it will not depend on number of years,,
For example let y be over x years, so Total sales over x years = 12*x*y=12xy
Now bi annual means 6-monthly or 2 times in a year......So, number of bi-annual in x years = 2x
So average biannual sales = $$\frac{12xy}{2x}=6y$$
So x doesn't matter, we just require y..

(1) The period includes exactly 4 years.
so x=4, but we don't require x.

(2) y = 500.

B
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Re: If the average (arithmetic mean) monthly sales of a department store   [#permalink] 13 Nov 2019, 23:05
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