Materials & Prep
Prepare one projected or board display of the market schedule used in the lesson. Students need paper or a notebook. No special materials are required.
Opening
Ask“A food truck has 10 burritos left at $5, but 30 students want one. What is likely to happen next, and why? Now imagine the truck has 30 burritos left and only 10 students want one. What is likely to happen?” Students first write a prediction, then compare with a partner. Ask two students to explain the pressure on the seller in each case. Accept everyday language such as “too many buyers compete” or “the seller lowers the price to attract buyers.”
ConnectExplain that students have already identified the central market relationship. When buyers want more than sellers offer, price tends to rise. When sellers offer more than buyers want, price tends to fall. Introduce the terms shortage, surplus, equilibrium price, supply, and demand only after students have made and explained their predictions.
Direct instruction
Display: Use this market schedule for burritos
Price: $2, $4, $5, $6, $8 Quantity demanded: 80, 60, 50, 40, 20 Quantity supplied: 20, 40, 50, 60, 80
ExplainAt $5, quantity demanded equals quantity supplied at 50 burritos. Neither buyers nor sellers have a reason created by excess demand or excess supply to push the price away from $5, so $5 is the equilibrium price.
Think aloud“Suppose the price is $2. Buyers want 80 burritos, but sellers offer only 20. The shortage is 60 burritos. Some buyers will be unable to purchase, and the competition among buyers gives the seller pressure to raise the price. As price rises, quantity demanded moves down the demand curve and quantity supplied moves up the supply curve. At $5, both quantities reach 50.” Emphasize the common error: the price does not move down to meet the larger quantity demanded. The shortage creates upward pressure on price.
Worked example“Suppose the price is $8. Quantity supplied is 80, but quantity demanded is 20. The surplus is 60 burritos. Sellers have 60 unsold burritos, so they have pressure to reduce the price. As price falls, quantity demanded rises and quantity supplied falls. The market moves toward $5.” Clarify that a change in the price causes movement along the existing curves. A change in another factor, such as income or production cost, would shift a curve.
Check for understandingStudents hold up 1 for “price rises,” 2 for “price falls,” or 3 for “no pressure to change” as you state: “At $4, Qd = 60 and Qs = 40.” Require the explanation: “There is a shortage, so buyers compete and price rises.” Then ask, “At $6, Qd = 40 and Qs = 60?” Expected response: “There is a surplus, so sellers reduce price.”
Guided practice
ModelOn the graph students already know how to draw, locate the intersection at $5 and 50 units. Narrate the interpretation rather than only labeling it: “The vertical coordinate tells us the equilibrium price, and the horizontal coordinate tells us the equilibrium quantity. The intersection is meaningful because it is where the amount buyers plan to buy equals the amount sellers plan to sell.”
Have studentsFor each situation, identify the imbalance, predict the direction of the price movement, and state what happens to the quantity demanded and quantity supplied as the market moves toward equilibrium.
- Price is $2: Qd = 80, Qs = 20.
- Price is $6: Qd = 40, Qs = 60.
- Price is $5: Qd = 50, Qs = 50.
Turn and talk“Why is saying ‘the demand curve moves up’ an inaccurate explanation for the first situation?” Listen for the distinction between a movement along a curve caused by a price change and a shift caused by a nonprice determinant. Circulate and press students to use the sequence “imbalance, pressure, price direction, movement toward equilibrium.”
ScaffoldProvide that sequence as a sentence frame: “At a price of __, buyers want __ and sellers offer __, creating a __ of __ units. This puts __ pressure on price because __. As price changes, quantity demanded __ and quantity supplied __.” Students may refer to the completed $2 example before completing the remaining cases.
Independent work or discussion
Students answer in complete explanations. They may draw a graph, but the written explanation must interpret the price movement.
- Use the schedule from direct instruction. Explain why $4 is not the equilibrium price and predict the direction of the next price movement.
- Use the schedule from direct instruction. Explain why $8 is not the equilibrium price and predict the direction of the next price movement.
- A sudden increase in demand means that at the current price of $5, buyers now want 70 burritos while sellers still offer 50. Identify the imbalance, predict what happens to price, and explain how the market moves toward a new equilibrium.
- Write one sentence distinguishing “a change in price” from “a shift in demand.”
CirculateLook for students who name only a curve or draw an arrow without explaining the market pressure. Ask, “Who has more than the market can provide, or who has unsold goods?” Then ask them to revise the explanation. Extension: Students who finish early may predict the likely effect of an increase in supply at $5, when Qd = 50 and Qs = 70, and explain why the new equilibrium price would tend to be lower.
Closing
Exit ticket“At a price of $4, a market has Qd = 60 and Qs = 40. Explain how supply and demand together determine what happens to the price. Include the terms shortage, quantity demanded, quantity supplied, and equilibrium.” A complete response states that the 20-unit shortage creates upward pressure, so price rises; as it rises, quantity demanded falls and quantity supplied rises, moving the market toward the equilibrium where the two quantities are equal.
Collect responses and quickly sort them into: explains imbalance and price direction, identifies imbalance but not the mechanism, or reverses the price movement. Use the pattern to plan the next lesson’s feedback.