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4.04 Representing information using matrices

Worksheet
Introduction to matrices
1

What is the special property of a square matrix?

2

State whether the following matrices are valid:

a
\begin{bmatrix} 3 & 6 \\ -2 & 8 \end{bmatrix}
b
\begin{bmatrix} 3 & 6 \\ -2 & 5 & -4 \end{bmatrix}
3

How many elements does a matrix with 4 rows and 5 columns contain?

4

How many elements are in the third column of a 7 \times 8 matrix?

5

How many elements are in the leading diagonal of a 4 \times 4 matrix?

6

Suppose M is a 4 \times 3 matrix.

a

How many rows does M have?

b

How many columns does M have?

7

If a column matrix contains 6 elements, how many rows does the matrix have?

8

How many columns does the identity matrix I_4 contain?

9

Write down the dimensions of the following matrices:

a
\begin{bmatrix} 1 & 4 \\ 8 & -3 \\ 9 & 0 \end{bmatrix}
b
\begin{bmatrix} 3 & -5 & 11 & 16 & -8 \end{bmatrix}
c
\begin{bmatrix} 7 \\ -3 \\ -2 \\ 6 \end{bmatrix}
d
\begin{bmatrix} 1 & 4 \\ -8 & 5 \\ -2 & 7 \\ 0 & 12 \end{bmatrix}
e
\begin{bmatrix} 1 & 4 & -8 \\ 11 & 17 & -15 \\ 21 & 10 & 9 \end{bmatrix}
f
\begin{bmatrix} 6 & 8 & 3 & -3 & 1 \\ 7 & 3 & 10 & 2 & 8 \\ 9 & 1 & -2 & 8 & 7 \\ 8 & -5 & 3 & 2 & 9 \end{bmatrix}
g
\begin{bmatrix} 8 & -1 & -4 & 9\\ 12 & 15 & -11 & 10 \end{bmatrix}
10

If a matrix has 10 elements, how many different dimensions could it possibly have?

11

A matrix with three less rows than columns has 54 elements. What are the dimensions of this matrix?

12

Write down the entry at a_{32} in the matrix \begin{bmatrix} 7 & 3 & -4 & 10\\ 12 & 0 & -11 & 10 \\ 8 & -2 & 9 & 11 \end{bmatrix}.

13

Where is 4 located in the matrix A = \begin{bmatrix} 9 & 2 & -6 & 8\\ 3 & 2 & 0 & -1 \\ 9 & 5 & 4 & 11 \end{bmatrix}.

14

Consider the matrices A = \begin{bmatrix} 4 & 1 & -2\\ 3 & 5 & 0 \end{bmatrix} and B = \begin{bmatrix} 6 & 2 \\ 3 & 0 \\ -1 & 9 \end{bmatrix}.

a

Find the value of a_{21} - b_{11}

b

Find the value of a_{13} \times b_{31}

15

Consider the following matrices:

A = \begin{bmatrix} 9 & 2 & 8 \\ 1 & 10 & 8 \\ 8 & -3 & 5 \end{bmatrix}, B = \begin{bmatrix} 9 & 2 & -6 & 8 & 10 \end{bmatrix}, C = \begin{bmatrix} 10 \\ 8 \\ -9 \\ 1 \end{bmatrix}, and D = \begin{bmatrix} 0 & 0 & 0 \\ 0 & 0 & 0 \end{bmatrix}

Which of these matrices is a:

a

Row matrix

b

Column matrix

c

Square matrix

d

Zero matrix

16

Write down the 3 \times 3 identity matrix.

Organising data into matrices
17

The following table shows the number of customers walking through the doors of two businesses over the long weekend:

a

Organise the data into a matrix. Let the position of each element be the same as the position in the table.

b

What are the dimensions of the matrix?

SaturdaySundayMonday
Florist14011098
Butcher150118135
18

The table shows the average temperature (in degrees Celsius) in two cities for each of the four seasons:

SummerAutumnWinterSpring
Perth30251728
Melbourne32261527

This data is organised into the following matrix:

\begin{bmatrix} 30 & 32 \\ 25 & 26 \\ 17 & 15 \\ 28 & 27 \end{bmatrix}
a

Do the rows of the matrix represent the temperatures for each season or for each city?

b

What are the dimensions of the matrix?

19

The following are the costs of a train ticket during different time periods:

  • Weekdays: \$6 peak, \$3 off-peak

  • Weekends: \$10 peak, \$7 off-peak

  • Public Holidays: \$16 peak, \$12 off-peak

a

Organise the data into a 3 \times 2 matrix.

b

Organise the data into a 2 \times 3 matrix.

20

Jack, a chef, is known for the following two recipes:

Crazy Cookie which contains:

  • 360 \text{ g} of yeast

  • 410 \text{ g} of salt

  • 340 \text{ g} of flour

  • 230 \text{ g} of sugar

  • 120 \text{ g} of honey

Scrumptious Surprise which contains:

  • 420 \text{ g} of yeast

  • 390 \text{ g} of salt

  • 330 \text{ g} of flour

  • 200 \text{ g} of sugar

  • 80 \text{ g} of honey

Organise the amounts into a 2 \times 5 matrix.

21

A long jump competition was down to four competitors in the final. Uther jumped 7.4 \text{ m}, 5.7 \text{ m} and 7.5 \text{ m} in his attempts. Yuri jumped 6.7 \text{ m}, 7.3 \text{ m} and 6.9 \text{ m}. Vincent jumped 7.1 \text{ m}, 5.9 \text{ m} and 6.8 \text{ m}, and Luigi jumped 5.6 \text{ m}, 6.1 \text{ m} and 6.3 \text{ m}.

Organise the data into a 3 \times 4 matrix.

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Outcomes

2.2.2.1

use matrices for storing and displaying information that can be presented in rows and columns, e.g. tables, databases, links in social or road networks

2.2.2.2

recognise different types of matrices (row matrix, column matrix (or vector matrix), square matrix, zero matrix, identity matrix) and determine the size of the matrix

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