Matrix multiplication notes

Here this is a small notes for matrix multiplication, It is very useful for matrix related algorithms. Lets start with normal multiplication,

For example we want to multiply 2 and 3, So normally we can do 2*3 = 6 OR 3*2 = 6 here you can see multiplication is commutative. But it is not always possible for matrix.

Please note that matrix multiplication is not commutative : M1 * M2 != M2 * M1

In matrix multiplication we have two matrixs one at left side and other one at right side like as per below

A (m X n) * B (n X k) = C (m X k)


We can only multiply two matrix if NUMBER OF COLUMN at left matrix is same as NUMBER OF ROW at right matrix.
Result matrix will be NUMBER OF ROW from left matrix and NUMBER OF COLUMN from right matrix.

Example :


See more example here