Lesson Plan

• Describe the concept of joint demand and identify examples of complementary goods.
• Explain how a price change in one complement shifts the demand curve of the related good.
• Analyse real‑world complementary markets and predict the direction of demand shifts.
• Evaluate policy or business strategies that exploit joint demand relationships.

• Projector and laptop for presentation
• Whiteboard and markers
• Printed handout with demand‑shift diagrams
• Worksheet containing the practice question
• Calculator (optional for quick calculations)
• Sticky notes for exit tickets

Begin with a quick poll: “If petrol prices fall, what happens to car sales?” Connect this to students’ prior knowledge of demand curves and set the success criteria: students will be able to illustrate and explain demand shifts for complementary goods.

1. Do‑now (5’) – Recall the effect of price changes on demand for substitutes and complements (short written response).
2. Mini‑lecture (10’) – Define joint demand, present the demand function, and highlight the negative cross‑price effect.
3. Graphing activity (10’) – In pairs, draw the demand curve for Good X shifting right/left when the price of Good Y falls/rises (using petrol‑car example).
4. Case‑study discussion (10’) – Groups analyse the provided table of complementary pairs and predict the direction of demand shifts.
5. Practice question (10’) – Individually answer the coffee‑sugar scenario; teacher circulates for formative feedback.
6. Summary checklist & exit ticket (5’) – Students list three key take‑aways on a sticky note and hand it in.

Recap the definition of joint demand, the direction of demand shifts, and how businesses or governments can respond. Collect exit tickets to gauge understanding, and assign homework: find a local complementary pair, describe a recent price change, and predict the resulting demand shift.