If you multiply two matrices: 3X5 * 5X2
you get a 3X2 matrix

What if you multiply 3X5 * 6X2 what matrix do you get?

Question

If you multiply two matrices: 3X5 * 5X2 
you get a 3X2 matrix

What if you multiply 3X5 * 6X2 what matrix do you get?

anonymous · Answer

One answer that I have seen is undefined but why?

anonymous · Answer

(AxB) * (CxD)

B and C have to be the same number in order to be able to multiply them
A and D give you the dimensions o the product

anonymous · Answer

@optiquest I know that but why can't you multiply them regardless of B and C

anonymous · Answer

I wish i had a good math nerd answer for you but i dont. The columns/rows wont line up right so you just cant. Maybe someone has a better answer.

anonymous · Answer

haha thanks my prof can be so picky I have to be ready for everything.

kinggeorge · Answer

In a more technical sense, matrices are a collection of vectors in a very certain manner, and when you multiply them, you're basically taking various dot products. If you have a vector of dimension 4, you can't dot product it with a vector of dimension not equal to 4.