3
How your jeans are made
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teacher's notes
3.2 Math activity
> Grade: 7th to 9th
> Subjects
Math
Sustainability
"Super Supply Chain Manager"
difficulty
This activity will encourage students to think about the whole supply chain of jeans. Also it will put them in the shoes of cotton farmers, factory managers, distribution managers and brand owners. All this through some mathematical problems that these professionals face everyday.
➤ Math
➤ Business
What is a "Super Supply Chain Manager"?
1
Divide your class in couples and give each a role from this list:
1. Cotton Farm Owner
2. Fabric Factory Manager
Print copies of the solution sheet you can find here and give it to the students.
Then ask them to solve the real life problems they will find in the table below, writing the solutions in the sheet.
Cotton Farm Owners will solve the problems in the box "Cotton Production".
Fabric Factory Managers will solve the problems in the box "Fabric Factory".
Cotton production
Fabric factory
The cotton Farm Owner
As a cotton farmer you are the first step in the making of a pair of jeans. You will provide the fibre that will later turn into denim. In order to grow that cotton you have to face a few challenges every season.
Follow the exercises and write the solution in the results sheet your teacher gave you.
problem one
Description
You need to start thinking about planting your seeds soon if you want to be on time to sell your cotton.
Questions
➤ How many seeds do I need this season?
➤ How much will it cost if I decide to buy organic seeds?
➤ How much will it cost if I decide to buy genetically modified seeds?
figures
➤ The land where I will plant the cotton is 4 hectares (ha)
➤ 1 seed of organic cotton costs 150DKK
➤ 1 seed of genetically modified (GM) cotton costs 200DKK
➤ I need 10 seeds per square meter (m2)
Conversion
1 ha = 10,000 meters
problem two
Description
If you want your plants to grow bigger and faster, you will need to buy liquid fertilizer whether you chose to plant organic or GM Cotton.
Questions
➤ How much fertilizer do I need in litres (l)?
➤ How much will it cost?
figures
➤ A gallon of liquid fertilizer costs 12.7 dollars
➤ The fertilizer instructions say that 1 litre (l) can cover 1 square meter (m2)
Conversion
1 $ = 6.6 DKK
1 gallon = 3,8 liter (l)
problem three
Description
Once the crop has grown, the harvesting season is ready to start. Let's get the collection season started!
Questions
➤ How much will the fuel for the tractors cost me?
figures
➤ I have 4 tractors
➤ Each tractor spends 20 litres (l) of diesel fuel every 1 ha.
Conversion
1 gallon of diesel fuel = 2 $
problem four
Description
To run my cotton farm I also need people. Depending on the jobs they do, they have different salaries. There are 3 different kind of positions:
Class A. Senior Operator.
Class B. Middle Operator.
Class C. Junior Operator.
Questions
➤ How much money do I spend each season in paying my employees (in DKK)?
figures
➤ I have 12 employees.
- 5 are class A.
- 4 are class B.
- 3 are class C.
➤ Class A workers earn twice as much as class C.
➤ Class B workers earn a fifth of Class A + the salary of C
➤ Class C workers earn 8,000$ for the season.
Conversion
1 $ = 6.6 DKK
The fabric factory manager
As a Fabric Factory Manager it is your responsibility to buy the cotton from the cotton farmers and turn it into denim fabric. After that you will sell this fabric to the manufacturing factories to turn denim into jeans. When producing the denim fabric you encounter different challenges every season.
Follow the exercises and write the solution in the results sheet your teacher gave you.
problem one
Description
Every season you buy cotton in bulk from the cotton farmers in order to turn the fluffy fibre into yarn and then into fabric.
Questions
➤ How many cones of thread will I be able to get with the cotton I bought this season?
➤ How much money (DKK) each cone costs me?
figures
➤ This season I bought 500 bales of cotton
➤ Each cone of thread is 6,000 meters (m)
➤ To produce 100m of thread I need 0.5kg of cotton
Conversion
1 bale of cotton = 180 kg
problem two
Description
Now it's time to weave the fabric! To weave denim we need 200 threads crossing horizontally and 200 threads crossing vertically for each 1.5m of fabric. Check the picture above ⇟
1.5m = 200 threads
Questions
➤ How many cones of thread do I need to weave 1 roll of denim?
➤ How many rolls of denim can I weave with the cones of thread I have?
figures
➤ Every roll of denim fabric is 60m long
Conversion
1.5m = 200 threads
problem three
Description
Now I know how much material it takes to produce my thread and my fibre. But how fast can I do it?
Questions
➤ How long will it take to weave 1 roll of denim fabric?
➤How long will it take to turn all the cotton I bought into cones of thread?
figures
➤ My spinning machines can spin the cotton into a cone of thread at a speed of 3m/sec.
➤ My weaving machines can turn the cones of thread into a roll of fabric at a speed of 4m/sec.
Conversion
problem four
Description
To run my cotton farm I also need people. Depending on the jobs they do, they have different salaries. There are 3 different kind of positions:
Class A. Senior Operator.
Class B. Middle Operator.
Class C. Junior Operator.
Questions
➤ How much money do I spend each season in paying my employees (in DKK)?
figures
➤ I have 12 employees.
- 5 are class A.
- 4 are class B.
- 3 are class C.
➤ Class A workers earn twice as much as class C.
➤ Class B workers earn a fifth of Class A + the salary of C
➤ Class C workers earn 8,000$ for the season.
Conversion
1 $ = 6.6 DKK
2
After the exercises discuss with your students the following questions.
➤ Does the price change if you choose organic options instead of genetically modified options?
➤ Do you think your decision at this stage will change the price of the jeans?
➤ How do you think you could be more sustainable as a cotton farmer?
➤ How do you think you could be more sustainable as a fabric factory manager?
Now you've learned about math in the supply chain!
GO to:
what is a supply chain?
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