SOLUTION: please help. every time i tried the equation in my calculator it never worked. question: the average number of MP3 players sold weekly at three different stores is given by the

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Question 634329: please help.
every time i tried the equation in my calculator it never worked.
question: the average number of MP3 players sold weekly at three different stores is given by the matrix. the selling price for the ipod is 240.00, the nano sells for 199.00 and the zen sells for 99.00. use the matrix multiplication to find revenue for each store.
ipod nano zen
circuitcity 50 75 80
bestbuy 45 79 63
target 58 67 98
Answer by jsmallt9(3758) (Show Source):
You can put this solution on YOUR website!
The only trick to this is figuring out how to set up the price matrix so that a) It can be multiplied with the 3x3 matrix of stores and items sold; and b) that the multiplication will multiply the right numbers together.

To multiply with the 3x3 matrix we will either use a 1x3 matrix on the left or a 3x1 matrix on the right. If we try a 1x3 matrix on the left of the 3x3, we end up multiplying a row of prices with a column of all the same device. (Try it out and see.) Multiplying with a 3x1 matrix on the right gets the right kinds of numbers multiplied: number of a device times the price of the device. So that is the way to go:

So CircuitCity's revenue: $34845
Bestbuy's revenue: $32758
Target's revenue: $36955