What a choice gives up

Paper packet. Every task here also exists on screen, where it is checked automatically; answers written on paper are not assessed by Nydus. When you are back at a device, enter your answers there.

1. What you will learn

2. Starting point

A resource limit determines which plans are possible. A supplied ranking tells us which possible alternative the decision maker prefers.

3. Words for this lesson

4. One choice leaves another possibility behind

Suppose a club has one activity period. It can use that period for drawing, a puzzle or a ball game, but only one activity can happen. The club chooses drawing. The puzzle and the game are not chosen. To understand the cost of the choice, ask what the club would have done instead if drawing were unavailable. The best available alternative it gives up is called its opportunity cost.

Opportunity cost concerns an alternative use of resources. In this example, the scarce resource is the activity period. Choosing drawing uses the time that could have been used for something else. The cost exists even if the drawing materials are free. A price is one kind of information about a choice, but it is not the complete definition of opportunity cost.

The word best requires information about the decision maker's preferences and circumstances. If the club prefers the puzzle to the game, the puzzle is its next-best option. If it prefers the game to the puzzle, the game is next best. We cannot read that ranking from the names of the activities alone. Our exercises supply an order of preference so you can identify the alternative without guessing what someone ought to enjoy.

Keep the actual choice separate from the alternative. The opportunity cost of drawing is not drawing itself. It is what the club gives up by using its resources for drawing. A clear answer names both: 'The club chooses drawing; its best available alternative is the puzzle.' This makes the comparison visible rather than leaving the reader to guess which option was selected.

Term	What it means
Alternative	Another possible use of the resources.
Preference ranking	An order of options from more to less preferred.
Opportunity cost	The best feasible alternative forgone by a choice.
Forgone	Given up because the resources are used for the chosen plan.
Feasible set	The plans that satisfy the stated constraints.

Another way: Read a supplied ranking carefully

A ranking puts options in order. Suppose a learner's stated order is reading first, painting second and a puzzle third. If the learner chooses reading and can complete only one activity, painting is the best unchosen alternative. The puzzle is lower in this supplied ranking. We do not add painting and the puzzle together, because the learner could not have completed both during the same period under the rule.

A ranking need not measure how strongly a person prefers one option. First, second and third tell us the order, but they do not tell us that the first option provides twice as much satisfaction as the second. Adding or subtracting rank numbers as if they were measured benefits would create information the ranking never supplied.

The actual choice may be stated as an option lower in the ranking. Suppose the same learner chooses the puzzle. Among the remaining feasible options, reading is best. Reading is then the opportunity cost of choosing the puzzle under the supplied information. We still identify the best forgone alternative correctly. We do not silently replace the stated choice with the option we think the learner should have selected.

In a real situation, an unexpected choice may suggest that our information about preferences or constraints is incomplete. In a small exercise, follow the information given and explain its limit. The calculation is not a judgment of the person's character or intelligence. It is a reconstruction of the alternatives under the stated conditions.

Another way: An impossible option is not available to give up

Suppose a group would most like to go swimming, next would like a park visit, and then would like an indoor game. The pool is closed during its free period. Swimming is therefore not a feasible option at that time. If the group chooses the indoor game, the best available alternative is the park visit, not swimming. A preferred possibility that cannot actually be chosen does not belong in this comparison.

The same idea applies to time, money, equipment and permission. An activity lasting two hours is not feasible in a one-hour period if it cannot be shortened. A model needing a tool that is unavailable may not be possible that day. Read these conditions before identifying the best alternative. Otherwise you may choose an attractive but impossible option as the cost.

Filtering the options is a separate step from ranking them. First identify which options fit the stated conditions. Then remove the chosen option from that feasible list. Finally, find the best of the remaining options using the supplied preferences. Keeping the steps separate helps prevent the chosen option or an infeasible option from being counted again.

Do not invent a constraint. If the case says the pool is open and the group can reach it in time, you should not rule it out because you personally dislike swimming. Your preference is not part of this group's stated ranking. Reasoning about another decision requires respecting the facts and ordering supplied for that decision.

Another way: The next-best alternative can be a plan

Sometimes an alternative is more than one activity. Suppose a forty-minute period allows either one forty-minute project or a twenty-minute story followed by a twenty-minute puzzle. The story-and-puzzle plan is a single feasible alternative use of the whole period. If the group prefers that plan to its other alternatives and chooses the project, that plan can be the opportunity cost.

This does not mean adding all unchosen activities is always correct. The two shorter activities form one alternative because they fit together under the time rule. A list containing four separate hour-long activities would not form a feasible alternative inside one hour. The set of available plans, not simply the number of attractive activity names, determines the comparison.

Our first exercises usually state that only one option can be chosen. Later exercises may explicitly allow a bundle of activities. Read which rule applies instead of carrying the earlier rule into every new case. A useful question is: could this proposed alternative actually replace the chosen plan while respecting the same resource limits?

The next-best alternative also depends on timing. A task that could be done tomorrow without affecting today's choice may not be forgone by today's plan. On the other hand, a one-time event happening now may be lost when the same hour is used elsewhere. Follow the case's description of which opportunities really compete. Opportunity cost is not a list of everything someone has ever wanted to do.

Another way: Price and opportunity cost answer different questions

Imagine you have six activity tokens. Entry to a craft session uses all six. You could instead use the six tokens for another session that you prefer to every other available use. The alternative session is the opportunity cost under this simple case. The six-token price helps establish which options are feasible, but it does not name what you give up unless we know the alternative uses of those tokens.

Time can be part of the choice too. A free event may take the same hour as another valued activity. A paid event may leave some money or time for another use. To compare complete plans fairly, include the relevant remaining resources and the alternatives they make possible. At this introductory level, the questions state the available plans clearly so you do not have to invent a whole budget.

It is also wrong to say that a money payment can never matter. Spending money can prevent another purchase, and that forgone use belongs in the opportunity-cost comparison. The point is that the concept is broader than a price tag, not that prices are irrelevant. Ask what the resources could have done in the best feasible alternative.

Nor is opportunity cost the same as regret. A person can be happy with a choice while recognizing what they gave up. If drawing was preferred to the puzzle, choosing drawing may be entirely consistent with the supplied ranking. The puzzle remains the next-best alternative. Identifying it helps explain the choice rather than proving the choice was a mistake.

Another way: Give the answer with its conditions

A strong explanation includes the resource limit, the feasible options, the actual choice, and the best remaining alternative. For example: 'Only one activity fits the hour. A and B are available; C is closed. The group chooses B. Since A is preferred to the other available alternatives, A is the opportunity cost.' This explanation is short but contains the information needed to check the result.

If two alternatives are tied for best, say that the ranking gives a tie. Do not invent a strict preference. If no ranking is supplied, explain that the next-best alternative cannot yet be identified uniquely. These are useful conclusions too. An exercise should not pretend to have a single exact answer when its information leaves several possibilities open.

Changing a condition can change the answer. Opening the pool adds a feasible option. Shortening a task may create a new combined plan. Learning a different preference order may change which forgone option ranks highest. Recalculate from the revised facts rather than assuming that an opportunity cost is permanently attached to an activity.

The method helps us describe a choice while leaving personal values visible. Economics can clarify what a given choice gives up under supplied preferences and constraints. It does not decide that every person must have the same preferences. That distinction lets us use careful reasoning without turning a classroom exercise into a judgment about whose interests matter.

5. Choosing a library activity

A library offers a forty-minute activity period. A group can choose A, a forty-minute comic workshop; B, a twenty-minute story followed by a twenty-minute puzzle; or C, a forty-minute outdoor activity. The group states its order of preference as C first, A second, B third. A weather closure makes C unavailable during this period. Both A and B are available and fit the forty minutes.

First filter by feasibility. C cannot be chosen now, despite its high ranking. A uses all forty minutes. B also uses all forty minutes because twenty plus twenty equals forty. B is one complete alternative plan, even though it has two parts. The group chooses A.

Remove the chosen plan from the feasible list. B is the remaining feasible alternative, so B is the opportunity cost of A under these conditions. It would be wrong to name C, because the weather closure makes it unavailable. It would also be wrong to count the story and puzzle as two additional forty-minute alternatives: together they are the one forty-minute plan B.

Now imagine the closure is lifted before the choice is made. With C available again, it becomes the best forgone option if the group still chooses A under the same stated ranking. The resource limit and preference order have not changed; the feasible set has. This comparison shows why an opportunity-cost answer must keep its conditions attached. It explains a particular choice rather than proving one library activity is best for everyone.

6. A tempting mistake

Do not add all unchosen activities when only one could replace the choice. Do include a combined plan when the case explicitly allows it and it fits the same limits.

7. Choose the first-ranked activity

8. An attractive option is unavailable

9. A two-part plan fits one period

10. A stated choice below the highest preference

11. Guided practice

Only one option fits. All of A,B,C are available. The preference order is A then B then C. A is chosen. Write the letter of the best feasible unchosen option and the number of feasible unchosen options.

12. Guided practice

All A,B,C are feasible, only one may be chosen, and the preference order is A,C,B. A is chosen. Fill the reconstruction.

13. Guided practice

14. Practice

Only one option fits. Ranking: D,A,C,B. D is unavailable; A,B,C are feasible. C is chosen. Write the letter of the best feasible unchosen option and the number of feasible unchosen options.

15. Practice

Only one option fits. A,B,C,D are all feasible. Ranking: C,D,A,B. B is chosen. Write the letter of the best feasible unchosen option and the number of feasible unchosen options.

16. Somewhere new

A library group can choose one forty-minute plan. A is a workshop; B is a twenty-minute story followed by a twenty-minute puzzle; C is a closed outdoor session. Ranking: C,B,A. Both A and B fit. The group chooses A. Write the letter of the best feasible unchosen option and the number of feasible unchosen options.

17. Lesson test

Lesson test: one question per skill, one attempt each, no hints. Your answers are checked when you submit.

18. Test question

Only one option fits. Ranking: B,D,A,C. B is unavailable. D,A,C are feasible, and D is chosen. Write the letter of the best feasible unchosen option and the number of feasible unchosen options.

19. What you can do now

Explain how to identify the best feasible alternative to a stated choice. Show a fresh example and check its result.

	Feasibility condition	Preference information	Actual choice
The room is available for one hour
The group prefers A to B
The group chooses B
The pool is closed at that time