DSE Economics | Comparative Advantage and Trade: Tutor Lesson Plan

2026-11-03

Tutor lesson-prep guides · Secondary Economics

Students compare hours when asked who makes cloth more cheaply, and pick the wrong country. This lesson converts every comparison into opportunity cost, forces both directions to be written, and proves mutual gain with total output before and after trade.

Objectives — Students can: (1) find that country A gives up 0.5 units of rice per unit of cloth while country B gives up 2; (2) assign cloth to A and rice to B; (3) state that the terms of trade must lie between 0.5 and 2; (4) show total output rising from 15 cloth and 15 rice to 20 and 20 with 40 hours each, and prove both gain when 6 cloth trade for 6 rice.

01 Prerequisites (3-minute check)

If any of these fails, fix it before the lesson starts.

Skill	Quick check	Pass mark
Opportunity cost	One hour makes 2 cloth or 4 rice; what does one cloth cost?	2 rice
Absolute advantage	What do we call producing more from the same resources?	Absolute advantage
Comparative advantage	What decides comparative advantage?	Lower opportunity cost
Terms of trade	What is the exchange ratio between exports and imports called?	The terms of trade

02 Lesson flow (60 minutes)

Time	Stage	Tutor does	Student does
0-8 min	Opening contrast	Ask whether the faster cloth maker must make cloth	Say that opportunity cost decides
8-20 min	Find opportunity cost	A needs 2 h for cloth, 4 h for rice	Compute both directions
20-32 min	Assign advantage	Compare 0.5 with 2	Name the good for each country
32-44 min	Terms of trade	Why the ratio sits between 0.5 and 2	Offer one workable ratio
44-52 min	Gains from specialisation	Compare totals with 40 hours each	Show 20 and 20 against 15 and 15
52-60 min	Independent practice	Three questions in eight minutes	Check and label errors

03 Teaching script (read it out)

Scene 1: Comparative advantage is about opportunity cost, never hours

Country A needs 2 hours for a unit of cloth, and those 2 hours could have made half a unit of rice, so one cloth costs 0.5 rice. Country B needs 4 hours, which could have made 2 rice, so one cloth costs 2 rice. Since 0.5 is below 2, A has the comparative advantage in cloth. Make students write both directions every time: cloth in rice, and rice in cloth, because the question may ask about rice.

Ask the student to separate the sentence for one cloth in rice from one rice in cloth.

Scene 2: The terms of trade must sit between the two opportunity costs

If A makes rice itself, one rice costs 2 cloth; B makes rice for only 0.5 cloth. At a ratio of one cloth for one rice, A buys rice for one cloth instead of two, and B sells rice for one cloth instead of half. Any ratio strictly between 0.5 and 2 leaves both better off. Students should be able to say which country sets each bound.

Ask for one ratio at which trade certainly fails, and which side walks away.

Scene 3: Prove the gain with totals, not with adjectives

With 40 hours each and self-sufficiency, each splits 20 hours per good: A gets 10 cloth and 5 rice, B gets 5 cloth and 10 rice, so the total is 15 and 15. After specialisation A makes 20 cloth and B makes 20 rice. Trading 6 cloth for 6 rice leaves A with 14 cloth and 6 rice, up 4 and 1, and B with 6 cloth and 14 rice, up 1 and 4. Both totals and both holdings must appear for a full answer.

Have the student recompute the holdings after trade and circle the gains.

04 Question types and worked steps

Type	Example	Steps	Answer
Opportunity cost	A needs 2 h for cloth, 4 h for rice	Same resource, both directions, express in units	One cloth costs 0.5 rice
Comparative advantage	Compare the cloth cost in both countries	Compute both, compare, lower wins	Country A in cloth
Range of terms of trade	A at 0.5 rice and B at 2 rice	Take the bounds, write the interval, give an example	Between 0.5 and 2 rice per cloth
Gains from specialisation	40 hours each, 6 cloth for 6 rice	Autarky output, specialised output, holdings after trade	Each gains 4 and 1 units

Sanity check (teach this): Order check: the two opportunity costs are reciprocals, so 0.5 times 2 equals 1, the quickest self-check available. Specialised output of 20 and 20 cannot fall below 15 and 15; if it does, the assignment is wrong. Holdings after trade must still add to the same 40 units of combined output as before.

05 Independent practice (3 questions)

Question	Answer	What to watch
A needs 3 h for cloth and 6 h for rice; cost of one cloth?	0.5 rice	Same resource comparison
If B costs 1.5 rice per cloth, is one rice per cloth workable?	Yes, inside 0.5 to 1.5	Check both sides lie inside
Specialised total from 15 plus 15	20 cloth and 20 rice	Did all 40 hours get used

06 Common mistakes and what to say

Mistake	Student writes	Say this
Comparing hours and calling it comparative advantage	“A needs only 2 hours, so A must have the comparative advantage”	“Fewer hours is absolute advantage; for comparative advantage you must say how much rice one cloth gives up.”
Computing only one direction	“One rice costs 0.5 cloth” instead of 2	“The two directions are reciprocals; your 0.5 cloth says rice is cheaper than cloth, which contradicts your own line above.”
Giving a single terms of trade	“The terms of trade must be one rice per cloth”	“The ratio is a range from 0.5 to 2; one is merely one workable value inside it.”
Claiming gains without totals	“Specialisation helps, so both gain”	“Show the numbers: 15 becoming 20, and how much each country holds afterwards.”

07 Homework (paper, section and question numbers)

Economics chapter index — Revise opportunity cost and the PPC, then questions 1 and 2
Opportunity cost and the PPC — Question 1 needs the production possibility curve
Price control and quotas — Compare intervention with free trade

08 Exit check (last 5 minutes)

Question	Answer	Decision
Cost of one cloth for A (2 h cloth, 4 h rice)	0.5 rice	Error: used absolute hours
Which country has the advantage in cloth	Country A	Error: compared hours
Workable range for the terms of trade	0.5 to 2 rice per cloth	Error: single point given
Specialised total output	20 cloth and 20 rice	Error: resources left idle

09 Tutor FAQ

Can trade happen when one country is faster at everything?

Yes. Absolute advantage across the board does not remove comparative advantage; different opportunity costs still allow mutually beneficial specialisation.

Who sets the actual terms of trade?

The range comes from the two opportunity costs, while bargaining power and market supply and demand pick the point inside it.

Must specialisation use every resource?

Questions usually assume full specialisation; in practice countries keep some diversity because of risk, transport costs and economies of scale.

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A TutorZone lesson-prep guide. Written by the TutorZone team; questions and lesson flow are original and are not taken from any school or publisher material.