Bunuel wrote:

Three shops that belonged to a chain were closed, and as a result the average (arithmetic mean) annual revenue per shop in the chain grew from $150,000 to $225,000. If the number of shops in the chain before the change was 8, approximately, what was the average annual revenue of the shops that were closed?

A. $25,000

B. $37,500

C. $58,333

D. $75,000

E. $91,666

if the average annual revenue of the 5 shops which are still open is 225,000, it means that they make a total of \(225,000*5= 1,125,000\) $

let's call the average annual revenue of the 3 shops that have been closed x.

therefore, they make a total of \(3*x\) $

We know that the total revenue of the 8 shops that were open has to be 150,000

Thus \(\frac{(3x+1,125,000)}{8} = 150,000\)

therefore \(x =25,000\) ===> answer A

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