Matrices review

Size of a Matrix

The size is determined by the number of rows x number of columns. Only like size matrices can be added or subtracted from one another.

Multiple Choice

How many rows are in a 7 x 3 matrix?

• 7

• 3

• 21

• 10

Multiple Choice

What is the size of the matrix below? Always do Rows x Columns.

• 3 x 4

• 4 x 3

Multiple Choice

What is the size of the matrix below?

• 0 x 1

• 1 x 0

• 3 x 3

• 3 x 0

Multiple Choice

What is the size or order of this matrix?

• 2 x 3

• 3 x 2

• 6 x 1

• 1 x 6

Multiple Choice

Dimensions?

• a

• b

• c

• d

Identifying Elements in a Matrix

We use subscript to identify the location of an element in a matrix. It is the name of the matrix followed by row x column. Rows are top to bottom and columns are left to right.

Multiple Choice

Which element is located in A₂₃?

• -3

• 5

• -9

• 2

Multiple Choice

What is the location of 5?

• A₁₂

• A₂₁

• A₂₅

• A₁₃

Multiple Choice

What is the value of element M_3,4?
(Think about what is in the 3rd row and 4th column)

• 34

• 42

• 37

• π

To add or subtract matrices A and B, add or subtract the corresponding elements.

Corresponding elements are elements in the same position in each matrix. 

Multiple Choice

What must be true in order to ADD two matrices?

• The dimensions must be equal.

• They must be square.

• The determinant can't equal 0.

Multiple Choice

Find A+B

• 8 10

  8 1

• 12 25

  7 1

• 10 30

  0 1

• can't answer two together because the rows don't match columns.

Multiple Choice

Subtract

• -9

  8

  3

  2

• -5

  8

  3

  2

Multiple Choice

Given these matrices find D - A

• None

scalar multiple looks like this

• A matrix

• 3A which means multiply all elements in matrix A by 3.

If this is matrix B determine...

• -2B

Multiple Choice

-2B would be which matrix below?

Multiple Choice

Multiply

• 20     15    -10 30     -5         0

• -20      15     -10 30     -5          0

• 1        8       3 11     4        5

• 20     -15     10 -30         5        0  

Multiple Choice

What do m, n, p and q equal in this scalar matrix multiplication?

• m=8, n=9, p=-4, q=4 

• m=15, n = -45, p=20, q=-5

• m=20, n=-5, p=15, q=-45

• m=-5, n=20, p=-45, q=15

Multiple Choice

What is the value of the variable in the equation?

Multiplying Matrices

Multiple Choice

Find the product of the two matrices.

• 17 12

  25 18

• 17 12

  12 6

• 17 12

  7 5

• 17 12

  10 12

Multiple Choice

Find the product of the two matrices.

• undefined

• -3   16

  17   12

  8   -10

• -3   16

    17  12

  -1   -3

Multiple Choice

• A

• B

• C

• D

Multiple Choice

• A

• B

• C

• D