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Mathematical Techniques - Matrix Algebra

Unit: Quantitative Analysis

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August 2025

1 Questions
Question 5a
​​Explain the following terms as used in the input-output analysis: 
 
(i) Primary inputs. 
 
(ii) Technical coefficients.
 
(iii) Final demand.


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December 2024

2 Questions
Question 6a
​​Using appropriate illustrations, explain the following terms as used in matrices: 
 
(i) Diagonal matrix.    

(ii) Scalar matrix.  


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Question 1c
​ ​ ​​The 2 x 2 matrices; A, X and B are given as follows:

\(A = \begin{bmatrix} 10 & 4 \\ 4 & 2 \end {bmatrix}; X = \begin{bmatrix} a & b \\ c & d \end {bmatrix}; A = \begin{bmatrix} 18 & 14 \\ 8 & 10 \end {bmatrix};\)

Required: Given that AX = B, find the values of a, b, c and d. 


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August 2024

1 Questions
Question 3a
​ ​ ​ ​ ​ ​ ​ ​​An economy produces food, clothing and shelter. To produce one unit of food, it requires 0.6 units from food sector, 0.2 units from clothing sector and 0.1 units from the shelter sector. To produce one unit of clothing, it requires 0.1 units from the food sector, 0.4 units from clothing sector and 0.2 units from the shelter sector. To produce one unit of shelter it requires 0.1 units from the food sector, 0.4 units from the clothing sector and 0.4 units from the shelter sector. 

Required: 

(i) Determine the matrix of technical coefficient (A). 

(ii) Compute the total output for food, clothing and shelter sectors to satisfy a final demand of 50 units of food, 400 units of clothing and 400 units of shelter.
       
     Assume that;

\(\displaystyle (1 - A)^{-1} = \frac{1}{0.086} \begin{bmatrix} 0.28 & 0.08 & 0.10 \\ 0.16 & 0.23 & 0.18 \\ 0.10 & 0.09 & 0.22 \end{bmatrix}\)
     
(iii) Account for the usage of clothing sector output determined in (a) (ii) above.


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December 2023

1 Questions
Question 3a
​​Highlight FOUR applications of Markov chain analysis in business and finance.


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April 2023

2 Questions
Question 5b
​​A trader purchased 7 cartons of apples and 4 cartons of bananas at a total cost of Sh.32,500 in the month of January.In the month of February, he purchased 9 cartons of apples and 6 cartons of bananas at a total cost of Sh.43,500.

Required:

Calculate the cost of a carton of apples and a carton of bananas using matrix algebra


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Question 3a
​ ​ ​ ​ ​ ​​Using the information given below, determine the level of output necessary from each sector to support a final demand of 500 units for sector X1, 1,600 units for sector X2 and 2,000 units for sector X3:

Inputs to
Output
\(X_1\)
\(X_2\)
\(X_3\)
Final demand (units)
\(X_1\)
40
40
40
   680
\(X_2\)
40
80
80
1,400
\(X_3\)
400
1,200
280
2,120


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December 2022

1 Questions
Question 3b
​ ​ ​​The banking industry in a given country is controlled by three banks Faida Bank, Akiba Bank and Ahadi Bank. As at 31 December 2020, Faida Bank controlled 30% of the market share, Akiba Bank controlled 50% of the market share and Ahadi Bank controlled 20% of the market share. 

A survey was conducted on the market shares of the three banks as at 31 December 2021 and revealed the following: 

  1. Faida Bank had retained 80% of its market share and lost 15% and 5% to Akiba Bank and Ahadi Bank respectively. 
  2. Akiba Bank had lost 10% and 20% of its market share to Faida Bank and Ahadi Bank respectively. 
  3. Ahadi Bank had lost 5% of its market share to Faida Bank and 5% to Akiba Bank. 
  4. There were no significant changes in the banking habits of the customers during the year ended 31 December 2021.

Required: 

(i) Determine the transition matrix from the above information. 

(ii) Determine the market shares of the three banks as at 31 December 2021. 

(iii) The steady state market shares of the three banks. 


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November 2019

2 Questions
Question 1c
​ ​​A small economy has two sectors, X₁ and X2 producing a single product for their internal and external demand (in units), as summarised in the following transaction matrix.

Production sector
Purchase sector
Consumer demand

X1
X2

X1
500
800
200
X2
600
1,400
400

The projected consumer demand changes to 400 units and 800 units for sector X₁ and X2 respectively. 

Required: 
The required gross output of each sector in order to meet the new demand.


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Question 4b
​ ​ ​ ​​A chemical reaction in a processing plant is given by: 

K = T² ​\(p^{-1}\)​     where: 
T is an input matrix. 
\(p^{-1}\)​ is an inverse of matrix P. 
K is an output matrix.

Given that T = ​\(\begin{bmatrix} 2 & 4\\ 2 & 0 \end{bmatrix}\)​ and

                  P =​\(\begin{bmatrix} 1 & 7\\ 0 & 4 \end{bmatrix}\)

Required: 
Calculate the output matrix K.


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May 2019

1 Questions
Question 1b
​​A salesman earns a fixed monthly basic salary and a commission that is directly proportional to the number of units sold in the month. During the months of February 2019 and March 2019, the salesman's total earnings were Sh.60,000 and Sh.70,000 respectively. The number of units sold by the salesman in the months of February 2019 and March 2019 were 100 and 250 respectively. During the month of April 2019, the salesman sold 400 units. 

Required: 
Using matrix algebra, determine: 
(i) The fixed monthly basic salary of the salesman. 
(ii) Commission earned per unit sold. 
(iii) Total earnings of the salesman in the month of April 2019.


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May 2018

1 Questions
Question 1c
​​

A certain firm has three main departments namely; steel, motor vehicles and construction. The three departments are interdependent. Each unit of output from the steel department requires 0.2, 0.3 and 0.4 units from steel, motor vehicles and construction departments respectively. Each unit of output from motor vehicles department requires 0.2, 0.4 and 0.2 units from steel, motor vehicles and construction departments respectively. A unit of output from the construction department requires 0.3, 0.4 and 0.1 units from steel, motor vehicles and construction departments respectively. The final demand of the firm comprises 20 million, 50 million and 30 million units of output from steel, motor vehicles and construction departments respectively.


Required:
(i) The technical coefficient matrix.
(ii) The total output of each department given that the Leontief's inverse matrix is as provided below:

\(\frac{1}{0.192}\)​ ​\(\begin{bmatrix} 0.46 & 0.24 & 0.26 \\ 0.43 & 0.60 & 0.41 \\ 0.30 & 0.24 & 0.42 \\ \end{bmatrix}\)

(iii) The change in the total output of the construction department, given that the final demand of steel department decreases by 2 million units and that of motor vehicles department increases by 10 million units whereas that of the construction department does not change.



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December 2017

2 Questions
Question 2d
​ ​​Excellent Products Limited manufactures four products, A, B, C and D, using four machines, M₁, M₂, M, and M;. The total outputs of the four products from the four machines are as shown below:

Output (units "000")
A
B
C
D
Machines
M1
12
12
6
13
M2
18
20
22
20
M3
16
15
12
18
M4
14
12
16
12

The company intends to assign the production of each output to a particular machine.

Required: 
Advise the management of Excellent Products Limited on the best assignment that will maximise production. 


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Question 1d
​ ​ ​ ​​Soda Baridi Limited has a computerised customer billing system. Customers' accounts are classified as being paid, delinquent or bad debt. The company has a total of 1,500,000 customer accounts. A computer program was developed to display transition of accounts among the three categories. The output from the program is summarised below:

To
Paid
Delinquent
Bad debt
Paid
285.000
15,000
0
From
Delinquent
20,000
700,000
30,000
Bad debt
0
0
450,000

The above transitions took place between 31 December 2015 and 31 December 2016.

 Required: 
The percentage of customers that will be in each of the three categories of accounts as at 31 December 2017. 


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May 2016

1 Questions
Question 1b
​​A certain audit firm has two categories of employees, auditors and assistant auditors. The total monthly salary of I auditor and 5 assistant auditors amount to Sh.456.755 whereas the total monthly salary of 3 auditors and 9 assistant auditors amount to Sh.985,005. The firm has a total of 6 auditors and 14 assistant auditors. The employees contribute 12 per cent of their monthly salaries towards their sacco society.

Required:
(i) The monthly salary of an auditor and an assistant auditor, using matrix algebra,
(ii) The employees' total monthly contribution towards their sacco society.


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November 2015

1 Questions
Question 1a
Star Manufacturers Limited specialises in the production of two products, A and B. The manufacturer sells the products at a fixed selling price to its customers. The following table shows the requirements for production of products A and B:

Product

Material (Kilogrammes)
Labour (Hours)
A
5
3
B
7
4
Available resources
13,400
7,800

Product A is sold for Sh.2.080 per unit whereas product B is sold for Sh.7.939 per unit. The variable costs of production are uncertain with the following margins of error:

Product

Labour/Hour (Sh.)
Material/Kilogramme (Sh.)
A
140
236
B
265
710
Error
±10%
±5%

Required:
Using matrix algebra, determine:

(i) The total expected revenue.
(ii) The expected maximum profit.
(iii) The expected minimum profit.


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Question 1b
​ ​ ​ ​ ​ ​​The research industry in your country has three market research firms namely X, Y and Z which provide research services. The following data has been collected in relation to the flow of clients among the three firms:
Inserted Image
Required:
(i) Convert the above data into a matrix of transition probabilities.
(ii) Estimate each firm's market share for 2015.


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