Concept : The Law of Demand
Objective : Drawing and Interpreting the Demand
Curve
Grade : 10
Time : 80 minutes
Materials : rulers, pencils graph paper, T-shirt
organisers
Activities
·
Explain to students that they will design a T-shirt and collect
data on how much other students would be willing to pay for the shirt.
·
Divide students into groups. Explain that they have four to six
minutes to create a design for a T-shirt. They should draw a quick sketch of
their design on the T- shirt organiser.
·
Once shirts have been designed, allow students five minutes to
survey their classmates regarding how much they would be willing to pay for
various designs. On the T-shirt organiser, students should make tick marks by
each price indicating the number of students who would pay that price. For
instance, if a student says that she would pay up to $12 for the shirt, a tick
mark should be made on the line next to $12. If a student says that he would
not buy the shirt at all, a tick mark should be made next to $0.
·
Students should then plot the data on a graph of Cost in Dollars
versus Number Sold. Teacher should make it clear to students that if a
classmate states that they would buy the shirt for a particular price, it
can be assumed that they would also buy the shirt for any price less than that.
For instance, if a student says he would pay $12 for the shirt, it can be
assumed that he would buy the shirt for $1, $3, $8, or any price up to $12.
This should be reflected in the graph. As a result, the graph will represent a
negative correlation; a possible graph is shown below.
·
When students have plotted the data, they should estimate a line
of best fit; that is, they should draw a line that roughly approximates the
data. As an example, a possible line of best fit is shown in the graph above.
·
Teacher
will ask students the following
questions based on their graphs
1.
How many shirts would you
sell if you gave them away for free or sell them at $0?
(Answers will vary,
depending on the students' data. Using the graph above, the straight line
implies that approximately 40 shirts would be sold at $0. However, students
should realize that the number is likely much higher - people who wouldn't be
willing to pay even $1 for the shirt might be willing to take it for free.)
2.
At what price will you sell no shirts?
(Answers will vary,
depending on the students' data. Using the graph above, it appears that $18 is
more than anyone would be willing to pay. Students should recognize that the x
intercept represents the point at which the price is too high.)
3. What happens to quantity
demanded as price increases?
(Students should be able to come to the realisation that as
price increases, quantity
demanded falls. From the graph above it can be observed that as price increases from $4 to $8 and then to
$12, quantity demanded falls from approximately
30 to 22 to 13 T-shirts respectively).
4. What happens to quantity
demanded as price decreases?
(Students should be able to infer from their
graphs that as price falls, quantity demanded
increases. From the graph above it can be seen that as price falls from $16 to $14 and then to $12, quantity
demanded falls from 4 to 7 to 13 t-shirts respectively).
·
Teacher will inform students that this relationship between
quantity demanded and price exemplifies the Law of Demand.
(The law of demand states
that as price increases consumers will demand less of the commodity and as
price decreases, consumers will demand more of the commodity.)
·
Teacher will ask students:
"What
effect do you think the law of demand has on your life?"
(Encourage students to come up with ideas
about how prices affect their demand of items, such as cellular phones, shoes
and clothes. Call on 3 to 5 students to share some of their thoughts with the
class).
T
Shirt Organizer
|
Design a T-shirt that
you might sell to your classmates. Draw a sketch of your T-shirt below.
For each price listed
below, record the number of your classmates who would be willing to pay that
amount for your T-shirt.
$0 _________________
1 _________________
2 _________________
3 _________________
4 _________________
5 _________________
6 _________________
7 _________________
8 _________________
9 _________________
10 _________________
12 _________________
14 _________________
16 _________________
18 _________________
20 _________________
25 _________________
30 _________________
|
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