Posted by **student** on Sunday, June 17, 2007 at 5:56pm.

When i have a matrix

4 X 4 and i have to multiply it by a

4 X 3

i know that the product size has to be a 4x 3

so do i do a row times column or how ?

It's easiest to learn using the notations for tensors. For any matrix X denote the entry in the i-th row and j-th column as:

X_{i,j}

Or, put differently, if you start at the top left corner and you take i steps downward and j steps to the right, you'll arrive at X_{i,j}

If X and Y are two matrices and Z = X Y, then the components of Z are given by:

Z_{i,j} = Sum over k of X_{i,k}Y_{k,j}

If X is the 4 by 4 matrix and Y is the 4 by 3 matrix, then the summation over k runs from 1 to 4, i can take values ranging from 1 to 4 and j can take values ranging from 1 to 3. Z is thus a 4 by 3 matrix.

## Answer This Question

## Related Questions

- Algebra II - I skipped algebra I so I never learned about matrices. If you had a...
- Math - Hi! I need help with these two questions. Thanks! :) 1.) Can we multiply ...
- Algebra - Need help with these-- 40. The graph of the following system yields ...
- Algebra 2 - Is it me or does this problem not make sense? (you can't solve it) 5...
- Math - I have a few questions about T-Matrix. In excel, I am suppose to work ...
- Math (matrices) - No one answered my matrix question. Let me rephrase: Let A, B...
- Matrix - How do you solve for this matrix. X*X^t=0? What matrix times its ...
- Math - Fine the size of the following matrix and its additive inverse matrix. ...
- Calc - A video games shop is analyzing its sales performance using matrices. ...
- Algebra 2..... - *Please explain on how to do each of these! 1. Let (x) be ...

More Related Questions