1. Umm Al-Qura University
بسم الله الرحمن الرحيم
Umm Al-Qura University
Health Sciences College at Al-Leith
Department of Public Health
Lecture (10)

2. Matrices Multiplication

3. Objectives: 1/ Define Matrix Multiplication Low.
2/ Explain How do you Multiple tow Matrices.
3/ Give an Example of Matrix Multiplication.

4. Multiplication of matrices
How do I multiply two matrices?
Two matrices [A] and [B] can be multiplied only if the number of columns of [A] is equal to the number of rows of [B] to give
If [A] is a mxp matrix and [B] is a pxn matrix, the resulting matrix [C] is a mxn matrix.

5. Example
Given
find
[C] = [A][B]
Solution

6. C11 = [ ]
C11 = [(5)(3) + (2 )(5) + (3)(9) ] = [ ] = 52

7. C21 =
C21 = [(1)(3) + (2 )(5) + (7)(9) ] = [ ] = 76

8. C22 =
C22 = [(1)(-2) + (2 )(-8) + (7)(-10) ] = [ ] = -88

10. Homework
If we have the following matrices
Find
1) A B
2) 3B + C
3) A C
4) 2B - A

12. Thanks
Radia