# MU123 Discovering Mathematics Assignment-The Open University UK

Submission instructions:
You will find instructions for completing TMAs in the ‘Assessment’ area of
the MU123 website. Please read these instructions before beginning work on this TMA.
you work on this one.
MU123 Discovering Mathematics Assignment-The Open University UK

Special instructions
Remember that you need to explain your reasoning and communicate your
ideas clearly, as described in Subsection 5.3 of Unit 1. This includes:
• explaining your mathematics in the context of the question
• the correct use of notation and units
• appropriate rounding.

Your score out of 5 for good mathematical communication (GMC) will be
recorded against Question 8. You do not have to submit any work for
Question 8.

Question 1
This question is based on your work on MU123 up to and including Unit 10.
(a) This part of the question concerns the quadratic equation

Question 2
This question is based on your work on MU123 up to and including Unit 10.
Aikta is the business owner of a small company which manufactures organic smoothies for local shops and restaurants. Because her product is organic, it has a short life span, so she needs to ensure that she is not over-producing, as waste product has a negative impact on profit margins. She decides to create an economic model using a computer program to predict how much smoothie should be produced in each production run (batch) to maximise profit.

MU123 Discovering Mathematics Assignment-The Open University UK

She is aware that if too little smoothie is made, the company will not meet
consumer demand and will miss the opportunity to sell more. If too much
smoothie is made, there will be an excess of unsold smoothie, which will go
bad, while still incurring the production cost to the company.

Aikta’s computer program models the situation as a quadratic equation of
the form y = ax 2 + bx + c,

where y represents the profit (in thousands of pounds) the company is
predicted to make, and x represents the amount of smoothie (in thousands of litres) produced in each batch. The values of a, b and c are determined by
the computer code that Aikta writes, and depend on various economic
measures and results of market research which Aikta inputs manually before each batch of smoothie is produced.

(a) Aikta wants to check that her code is working correctly. She inputs
some test values and runs the code to simulate the model. The quadratic equation produced is

y = 4.862x 2 − 7.211x + 4.836.

By considering the coefficient of x 2, explain why Aikta’s code must contain an error.

(b) Aikta corrects the error, and runs the program again. This time the

y = −7.291×2 + 5.771x − 0.502.

In this part of the question, you are asked to consider the parabolic
graph modelled by the equation y = −7.291x + 5.771x − 0.502.
(i) Explain mathematically why the y-intercept is −0.502.
(ii) Using the context of the question, give one possible reason why the
y-intercept would be negative.
(iii) Use the quadratic formula to find the x-intercepts. Give your
answers correct to three decimal places.
(iv) According to Aikta’s model, what is the minimum amount of
smoothie the company needs to produce in order to break even
(v) The company sets a target of making £600 profit in the next batch.
The company decides to produce 500 litres of smoothie (i.e.
0.5 thousand litres of smoothie). According to Aikta’s model, will
the company exceed or fall short of its target? Explain your answer.

MU123 Discovering Mathematics Assignment-The Open University UK

Question 3
This question is based on your work on MU123 up to and including Unit 11.
Joe works for a small company which employs 20 people. He is interested in
investigating the effect of the COVID-19 pandemic on the number of hours
worked by the company’s employees. To get an initial sense of what the
effect might be, he picks the first full working week in June 2019 and
compares it with the equivalent week in June 2020. For each of the two
chosen weeks, he downloads the number of working hours logged by each
employee. The raw data are shown in Table 1.

Table 1 Number of hours worked in the first full working week of June

(a) Joe considers displaying the data as a pair of dotplots. Do you think
this is a good idea for these particular datasets? Give a brief reason for

(b) Joe decides to create a box plot for each year as displayed in Figure 2.

With reference to Subsection 1.2 of Unit 11, state three ways in which
Joe could improve the clarity of his presentation of the boxplots.

(c) Joe can’t remember which boxplot belongs to which year. State one way
in which he could check by looking at the raw data for each year.

(d) Joe realises that the top boxplot represents the data for 2020 and the
bottom boxplot represents the data for 2019. He tries to interpret what
the data is telling him by making the statements below. For each one,
state whether you agree or disagree with Joe’s interpretation, and
explain why you think he is correct or incorrect.
(i) ‘On average, employees worked more hours in 2020 than in 2019.’
(ii) ‘There was greater variability in the number of hours worked in 2020 compared with 2019.’
(iii) ‘More than half of employees in 2020 worked more than the median
number of hours.’
(e) Use the boxplot for 2020 to say whether the data are symmetrical or
skewed. If the data are skewed, then state whether they are skewed to
the left or skewed to the right, explaining your reasoning briefly.
(f) Joe creates (poorly presented) histograms for each of the two datasets,
shown in Figure 3 and Figure 4 below.

(i) Which histogram belongs to the data for 2020 – Figure 3 or
(ii) Comment on one aspect of the comparison of data from the two
years that can be seen more easily on the histograms than on the
box plots.
(iii) Comment on one aspect of the comparison of data from the two
years that can be seen more easily on the boxplots than on the
histograms.

MU123 Discovering Mathematics Assignment-The Open University UK

Question 4
This question is based on your work on MU123 up to and including Unit 12.
(a) Figure 5 shows a sketch of a triangle, where all side lengths are
measured in centimetres. Find the length of the side marked x, giving

(b) Triangle DEF has a right angle at E. The length of side DE is 4.2 mm,
and the length of side DF is 6.6 mm. Find ∠EDF, giving your answer
correct to the nearest degree.

You may find it useful to sketch triangle DEF in your answer.

(c) (i) Figure 6 shows the triangle ABC, with all side lengths measured in

(ii) Find the area of triangle ABC in Figure 6, giving your answer correct to the nearest square centimetre.
(ii) Use your answer from part (d)(i) to find the area of a sector of a
correct to two significant figures.

Question 5
This question is based on your work on MU123 up to and including Unit 12.

Laura is designing a computer game which simulates space exploration. She
controls a spaceship which she wishes to pilot from Earth to a neighbouring
star called Arcturus.

Arcturus lies 36.7 light-years away (in a straight line) from Earth. However,
Laura cannot pilot the spaceship in a straight line towards Arcturus, as a
comet lies in her path. Starting from Earth, she sets out in a straight line.
She chooses a direction which avoids the comet, but still gets her slightly
closer to Arcturus.

Once she has travelled in a straight line for 9.1 light-years, she stops the
spaceship. From her current position, she can see both Earth and Arcturus,
and the spaceship’s instruments show that the angle between her lines of
sight to Earth and Arcturus is 110◦

(a) Sketch a diagram of the situation, showing the points E for the position
of Earth, A for the position of Arcturus and S for the current position
of the spaceship. Mark in the angle and the lengths (in light-years) that
you are given. Join the three points with line segments to make the triangle EAS.
(b) Laura would like to calculate the distance between the spaceship’s
current position and Arcturus. She realises that in triangle EAS she
has two side lengths and an angle. She mistakenly concludes that she
can solve her problem with a single direct application of the Cosine
Rule, like in Example 9 in Subsection 2.2 of Unit 12.
Explain, as if directly to Laura, why she can’t use the Cosine Rule
directly in this way to solve her problem.

(c) (i) Use the Sine Rule to find the angle at A. Give your answer correct
to the nearest degree.
(ii) Use your answer to part (c)(i) to find the angle at E. Give your
answer correct to the nearest degree.
(iii) Use the Cosine Rule and your answer to part (c)(ii) to find the
correct to two significant figures.

MU123 Discovering Mathematics Assignment-The Open University UK

Question 6
This question is based on your work on MU123 up to and including Unit 12.

In this question, you are asked to comment on a student’s attempt at
incorrect attempt first, then answer the questions below.

The Question
Yusuf is a building manager for an office which has a room full of computer servers. The servers must be kept cool with a fan, or else they will overheat and malfunction. Yusuf buys a fan which oscillates to cover an angle of 52◦. The servers he would like to keep cool span the length of a wall which is 5 metres wide. Assume that the fan is placed centrally with respect to the room’s width.

Yusuf sketches the situation in Figure 7, where all lengths are measured in metres. The point F represents the fan’s position. Points A and B are the furthest reaches of the room’s width. The point C is the centre point of the room’s width. The length of F A is equal to the length of F B. Angle AF B is 52◦, so angle AF C is 26◦

Assuming the fan is strong enough, how far from the centre point C should the fan stand in order to be able to utilise the full 52◦ oscillation to cool the whole wall’s width?

The student’s incorrect attempt
We first calculate the angle at A, using the fact that all three angles
in triangle ACF add up to 180o . So we have
A = 180 (90 + 26) = 64.
So the angle A is 64o

Using the Sine Rule in triangle ABF, we have

So the length of BF is 5.7 m (to 1 d.p.).

The length of BF is the same as the length of AF, and triangle ACF is right-angled, so we have

Therefore, to 2 decimal places, the fan should be placed at least 6.34 m
away from the centre of the room.

(a) Look at the student’s answers for the lengths BF and CF. Using what
you know about right-angled triangles, and without performing any
further calculations, explain how you know that at least one of these
calculated lengths must be wrong.

(b) There are two places in the student’s attempt where a mistake has been
made. Identify these mistakes, and explain, as if directly to the student,
why, for each mistake, their working is incorrect.

(c) Do you think the student’s approach to solving the problem is the most

(d) Write out your own solution to the problem, explaining your working.

Question 7
In this question you are asked to reflect on how your studies so far on
MU123 fit in with your wider study interests and future study plans.

(a) Choose one topic from MU123 that you think is relevant to your wider
study interests. Explain why you think your chosen topic is particularly
interesting and/or relevant to your future study plans.

If you don’t find any of the topics from MU123 interesting or relevant to
your future study plans, then explain why.

(b) Do you feel confident in your chosen topic? If so, describe one step you
could take to maintain your confidence in years to come. If not, describe
one step you could take to help you work more confidently in that topic.

If you did not choose one specific topic in your answer to part (a),
choose one topic from MU123 in order to answer this part. For example,
you could choose a topic which you found particularly challenging.

Question 8
A score out of 5 marks for good mathematical communication over the entire TMA will be recorded under Question 8.

MU123 Discovering Mathematics Assignment-The Open University UK