Most people are familiar with how to multiply two matrices together. However, an alternate form of multiplication known as tensor multiplication exists as well, and works more like you would expect matrix multiplication should. Let
A be a
p ×
q matrix and
B be an
n ×
m matrix, where neither
A nor
B is a 1 × 1 matrix. Then the tensor product
is a
pn ×
qm matrix formed by replacing each element
aij in A with the matrix (
aij) ·
B. Two examples are shown below, which also demonstrate that, like normal matrix multiplication, tensor multiplication is non-commutative:
Note that there is no restriction that the number of columns in the first matrix must equal the number of rows in the second, as there is with normal matrix multiplication. The object of this problem is to determine the number of ways (if any) a given matrix can be formed as a result of a tensor multiplication.