UNIT 1 · CHOICE AND TRADE-OFFS
Why isn't opportunity cost just the money you spend?
Connect the best forgone alternative to a PPC. Distinguish money spent, total opportunity cost and opportunity cost per unit, then try an existing original question.
In this guide · 6 sections
A note from your study buddyFirst ask what you give up to get something. Then check whether the question asks for a total or a cost per unit.
01 / DIRECT ANSWER
Opportunity cost is the best alternative you give up
The opportunity cost of a choice is the value of the next-best feasible alternative you forgo. It can involve money, time, leisure or another good. It is not the sum of every option you did not choose.
Suppose you can spend the next two hours either practicing for AP or working a part-time shift. If the shift would have paid 100 yuan, choosing practice means giving up that income. Free practice can still have an opportunity cost. The relevant value depends on the alternatives and conditions in the question.
Opportunity cost focuses on the forgone alternative. Out-of-pocket cost focuses on money actually paid. If a question asks about the former, a list of bills alone may leave out a relevant sacrifice.
02 / ORIGINAL WORKED EXAMPLE
Along a PPC, count what decreases
Assume resources and technology are unchanged. An economy has these two efficient production combinations on its production possibilities curve (PPC):
| Combination | Bread (portions) | Juice (cups) |
|---|---|---|
| A | 4 | 18 |
| B | 7 | 12 |
- The good gained: bread increases by 7 − 4 = 3 portions.
- The good forgone: juice decreases by 18 − 12 = 6 cups.
- The total opportunity cost of this change is 6 cups of juice.
- If asked for the average opportunity cost of one additional portion of bread over this interval, divide 6 by 3: 2 cups of juice per portion of bread. This interval average does not establish a constant cost at all production levels.
03 / COMMON MISTAKES
Check which kind of cost the question asks for
The additional 3 portions of bread are what the economy gains. Express opportunity cost in the forgone juice, with units.
6 cups of juice and 2 cups of juice per portion of bread answer different questions. Read the requested quantity before calculating.
A movement along a fixed PPC reallocates resources. Better technology or more resources can expand production possibilities. Starting inside the curve, using idle resources can also increase both outputs.
04 / YOUR TURN
Now calculate the trade-off between goods X and Y
This PPC question comes from the existing original bank. Its graph and options belong to the same revision, and the existing practice server checks your answer.
ORIGINAL MCQ · NO ACCOUNT NEEDED
An economy produces combinations of Good X and Good Y along the production possibilities curve shown in the graph. If society reallocates its fully utilized resources to expand the output of Good X from 2 units (Point R) to 5 units (Point S), what is the resulting opportunity cost?
Answers and explanations are returned by the practice server after submission. This article does not save guest practice history.
05 / KEEP GOING
Keep the units attached to your reasoning
Continue with existing Unit 1.3 original questions. Distinguish a trade-off along the curve, idle resources inside it and an outward shift. Identify what is forgone before counting it.
SOURCES & SCOPE
Sources and scope
Course scope was checked against these primary sources on 2026-10-17. Worked examples, explanations and study advice are by AP Exam Kit, which is not affiliated with or endorsed by College Board.
- College Board · AP Microeconomics CED (Fall 2026) ↗
Topic 1.3, MKT-1.C; PDF page 43 / printed page 35 includes calculating opportunity cost using PPCs and tables. The everyday example, numerical walkthrough and study sequence here are AP Exam Kit teaching content.
AP Exam Kit authored this supplemental guide and checked its cited course sources. Independent teacher review has not been completed; this is not official College Board material.