Question 62112
Explain how to determine whether (a) two matrices can be: added or substracted.
The two must have the same number of rows and same number of columns.
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(b) two matrices can be multiplied together. 
If you are multiplying AB, B must have the same number of
rows as A has columns.
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(c) Consider the matrices C and D listed below. Matrix c shows the number of healthy vegetables an average plant will produce in different climate zones. Matrix D shows the average number of seeds produced by a vegetable of each type. Clearly explain how the two matrices can be multiplied together to obtain a product which is meaningful. Describe the meaning of the product. (You do not need to find the product of the matrices.)
Zone 3 - Zone 4 - Zone 5
Tomato 145 - 175 - 211
C = Cucumber 12 - 16 - 28
Green Pepper 8 - 14 - 24
Tomato - Cucumber - Green Pepper
D = Average Number 64 - 75 - 49
Seeds per vegetable

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Matrix C is 3 x 3 (veggies x zones)
Matrix D is 1 x 3 (ave # of seeds x veggie)
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Multiply D times C to get aver # of seeds for these veggies per zone.
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Cheers,
Stan H.