Subject
: Economics
Class
:X
Time Aloccation : 2 x 45 Minute
Today's Lesson
Standar Kompetensi dan Kompetensi Dasar
STANDAR KOMPETENSI
:
3. Memahami konsep ekonomi dalam kaitannya
dengan permintaan, penawaran, harga
keseimbangan, dan pasar
Kompetensi Dasar
3.2. Menjelaskan hukum permintaan dan
hukum penawaran serta asumsi yang
mendasarinya.
1. Menginterpretasikan hukum permintaan dan
penawaran.
2. Menginterpretasikan asumsi yang mendasari hukum
permintaan dan penawaran.
3. Menggambar kurva permintaan dan penawaran yang
bergerak dan bergeser.
4. Membuat fungsi permintaan dan fungsi penawaran
berdasarkan hukum permintaan dan penawaran.
The Law of Demand
The law of demand says: “If price
increases, the demand for goods or
services will decrease. On the contrary,
when price decreases, the demand for
goods or services will increase, ceteris
paribus”.
Price   Quantity Demand 
Price   Quantity Demand 
P ↑  Qd ↓ or P ↓  Qd ↑
“relationship between price and demand
is inversely”
Example: Kartini’s Demand Schedule
Price of Ice-Cream
Cone (Rp)
Quantity of Cones
Demanded
12.000
10.000
8.000
6.000
4.000
2.000
0
0
2
4
6
8
10
12
Copyright © 2004 South-Western
Demand Curve
Price of
Ice-Cream Cone
Rp. 12.000
10.000
1. A decrease
in price ...
8.000
Price of IceCream Cone (Rp)
Quantity of Cones
Demanded
12.000
10.000
8.000
6.000
4.000
2.000
0
0
2
4
6
8
10
12
6.000
4.000
2.000
0 1 2 3 4 5 6 7 8 9 10 11 12 Quantity of
Ice-Cream Cones
2. ... increases quantity
of cones demanded.
Copyright © 2004 South-Western
The Law of Supply
The law of supply says: “If the price of
goods or services increases, the quantity
of goods or services supplied also increase,
and on the contrary, if the price of goods
or services decreases, the quantity of
goods or services supplied also decreases,
ceteris paribus”.
Price   Quantity Supply 
Price   Quantity Supply 
P ↑  Qs ↑ or P ↓  Qs ↓
“relationship between price and supply is
directly proportional”
Example: Krisna’s Supply Schedule
Price of Ice-Cream
Cone (Rp)
Quantity of Cones
Supplied
2.000
4.000
6.000
8.000
10.000
12.000
0
1
2
3
4
5
Copyright © 2004 South-Western
Supply Curve
Price of
Ice-Cream
Cone
Rp.12.000
1. An
increase
in price ...
10.000
Price of IceCream Cone (Rp)
Quantity of Cones
Supplied
2.000
4.000
6.000
8.000
10.000
12.000
0
1
2
3
4
5
8.000
6.000
4.000
2.000
0
1 2
3
4
5
6
7
8
9 10 11 12 Quantity of
Ice-Cream Cones
2. ... increases quantity of cones supplied.
Copyright©2003 Southwestern/Thomson Learning
Assumption of the law of
demand and supply
Assumptions underlying the law of
demand and supply of other factors being
equal that changes only the price of the
goods themselves. This condition is
known as “Ceteris paribus”
Factors - Factors That Affect Demand





Level of Income
Population
People’s Taste
People’s Prediction
Price of Subtitutive and Complementary Goods
Factors - Factors That Affect Supply





Production Cost
Number of Producers
Natural Disasters
Technology
Price of Other Goods and Services
Demand Curve Shifts
Price of
Ice-Cream
Cone
Increase
in demand
Decrease
in demand
Demand
curve, D2
Demand
curve, D1
Demand curve, D3
0
Quantity of
Ice-Cream Cones
Example: If Income Increase
Price of IceCream Cone
$3.00
An increase in
income...
2.50
Increase
in demand
2.00
1.50
1.00
0.50
D1
0 1
2 3 4 5 6 7 8 9 10 11 12
D2
Quantity of
Ice-Cream
Cones
Example: If Income Decrease
Price of IceCream Cone
$3.00
2.50
An increase in
income...
2.00
Decrease
in demand
1.50
1.00
0.50
D2
0 1
D1
2 3 4 5 6 7 8 9 10 11 12
Quantity of
Ice-Cream
Cones
Supply Curve Shifts
Price of
Ice-Cream
Cone
Supply curve, S3
Decrease
in supply
Supply
curve, S1
Supply
curve, S2
Increase
in supply
0
Quantity of
Ice-Cream Cones
Copyright©2003 Southwestern/Thomson Learning
Determine The Demand And Supply Functions
Formula:
Initial Quantity
Product
Initial Price
P – P1
P2 – P1
Prices After
The Change
Q – Q1
=
Q2 – Q1
Quantity After
The Change
Demand and Supply Functions
Demand Function:
PD = a - bQ
PD = 8.000 – 0,02 Q
Supply Function:
PD = a + bQ
Ps = 8.000 + 0,02 Q
Demand Function
Coefficient
Price
P = a - bQ
constants
Quantity
The Law of Demand
Supply Function
Coefficient
Price
P = a + bQ
Quantity
constants
The Law of Supply
Example
Price
Quantity
4500
175.000
3500
225.000
how its function
P – 4.500
3.500 – 4.500
P – 4.500
=
=
Q – 175.000
225.000 – 175.000
Q – 175.000
50.000
1000
50.000 P – 225.000.000 = –1.000 Q + 175.000.000
50.000 P
= –1.000 Q + 400.000.000
PD
=
8.000 – 0,02 Q
Sekian
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• Terima kasih