Yes, the matrix product $AB$ is defined when $A$ has dimensions $n\times m$ and $B$ has dimensions $m\times k$ for any integers $n,m,k$, and the resulting matrix will have dimensions $n\times k$. – 2011-05-02
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How about a (3X2) * (5X3) is this a 3x5?... this is my last question to finally understand this – 2011-05-02
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@edprof: that product is not defined in that order (the dimensions $2$ and $5$ on the inside don't match). In the other order, it's $5 \times 2$. – 2011-05-02
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@edprof: As Qiachu and matt have said, the right-most dimension of the matrix on the left must match the left-most dimension of the matrix on the right, or else the product is meaningless. The dimension on the left represents the number of rows in a matrix; the dimension on the right represents the number of columns of the matrix. Check out the link provided by DJC for more details. – 2011-05-02
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@All: why did 'community' bring this back to the front page? – 2011-06-04
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@mixedmath, my understanding is that "Community" somehow selects questions where no answer has been accepted and resurrects them in the hope that the questioner will find some answer, old or new, acceptable. – 2011-06-04