Katherine P. answered • 03/04/13

Positive, Effective, and Experienced Math Tutor

The formula you want to remember (or write in your notes) is:

**( m x n ) x ( n x p ) = ( m x p )**

The columns of the first matrix (n) need to equal the rows of the second matrix (n).

In your case, you have:

DC = (3 x 5) x ( 5 x 1)

Applying ( m x n ) x ( n x p ) = ( m x p ), you get the dimensions of DC:

( 3 x 1)

Hope that helps!