1. The problem statement, all variables and given/known data This is a seemingly simple problem. All I have to do is multiply two matrices: [ 1 0 ] [ 0 1 ] (A) and [ 2 ] [ 3 ] (B) 3. The attempt at a solution Because the matrix A has the same number of columns as matrix B has rows, and because matrix A is an identity matrix, I would expect the answer to just be matrix B. But the back of the book says the answer does not exist which boggles me. Can anyone share any useful insight?