High School Economics Quiz: Marginal Decision Rule
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Marginal Decision RuleQuestion 1 of 18

A person is at an all-you-can-eat buffet for which they paid a flat fee of $20. They are considering whether to go back for a third plate of food. Which statement best explains a rational decision to stop eating after two plates?

The total benefit from all three plates would likely be less than the $20 cost of the meal.
The average cost per plate increases as the consumer's satisfaction with each plate decreases.
The money paid for the buffet is a sunk cost, therefore any additional consumption has zero benefit.
The marginal utility from the third plate is outweighed by its marginal cost, such as physical discomfort.
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High School Economics Quiz

High School Economics Quiz: Marginal Decision Rule

Practice Marginal Decision Rule in High School Economics with focused quiz questions that help you check what you know, review explanations, and build confidence with test-style prompts.

What this quiz covers

This quiz focuses on Marginal Decision Rule, giving you a quick way to practice the rules, question types, and explanations that matter most for High School Economics.

How to use this quiz

Try each quiz question before looking at the correct answer. Use the explanations to review missed ideas, then come back to similar questions until the pattern feels familiar.

All questions

Question 1

A person is at an all-you-can-eat buffet for which they paid a flat fee of $20. They are considering whether to go back for a third plate of food. Which statement best explains a rational decision to stop eating after two plates?

  1. The total benefit from all three plates would likely be less than the $20 cost of the meal.
  2. The average cost per plate increases as the consumer's satisfaction with each plate decreases.
  3. The money paid for the buffet is a sunk cost, therefore any additional consumption has zero benefit.
  4. The marginal utility from the third plate is outweighed by its marginal cost, such as physical discomfort. (correct answer)
Explanation: The monetary cost of the third plate is zero, but there are non-monetary marginal costs. These include the opportunity cost of time and the potential physical discomfort from overeating. A rational consumer stops when the marginal benefit (utility) of the next plate is less than its marginal cost (including non-monetary costs). The $20 fee is a sunk cost and irrelevant to this specific decision.

Question 2

A student values their leisure time at $15 per hour. For an upcoming exam, they estimate the marginal benefit from the first hour of studying is $25, the second hour is $20, the third hour is $15, and the fourth hour is $10. To maximize their net benefit, how many hours should the student study?

  1. 2 hours, because this is the last point where the marginal benefit is clearly greater than the marginal cost.
  2. 3 hours, because for every hour up to this point, the marginal benefit is greater than or equal to the marginal cost. (correct answer)
  3. 4 hours, because this maximizes the total benefit gained from studying for the exam.
  4. 0 hours, because the value of leisure is high and studying provides a non-monetary benefit.
Explanation: The marginal decision rule states one should continue an activity as long as the marginal benefit (MB) is greater than or equal to the marginal cost (MC). Here, the MC is the opportunity cost of leisure, 15/hour.Hour1:MB=15/hour. Hour 1: MB=25 > MC=15.Hour2:MB=15. Hour 2: MB=20 > MC=15.Hour3:MB=15. Hour 3: MB=15 = MC=15.Hour4:MB=15. Hour 4: MB=10 < MC=$15. The student should study for 3 hours, as the fourth hour's marginal benefit is less than its marginal cost.

Question 3

A city council is deciding how many public parks to build. The marginal benefit of each additional park decreases as more are built, while the marginal cost is constant. After analysis, the council decides to build 3 parks. Which of the following must be true for this to be the optimal decision?

  1. The marginal benefit of the 3rd park is greater than or equal to its marginal cost, but the marginal benefit of a 4th park would be less than its marginal cost. (correct answer)
  2. The total benefit generated by the 3 parks is substantially greater than the total cost of building and maintaining all 3 parks.
  3. The marginal benefit of the 3rd park is exactly equal to its marginal cost, creating an equilibrium point for public goods.
  4. The average benefit per park is maximized at 3 parks, ensuring the most efficient use of tax dollars across all parks.
Explanation: The optimal quantity of any activity is found where the marginal benefit of the last unit is greater than or equal to its marginal cost (MB ≥ MC), and the marginal benefit of the next unit is less than its marginal cost (MB < MC). The other options represent common errors: focusing on total benefit (B), assuming an exact equality which isn't necessary for discrete units (C), or incorrectly using average benefit (D).

Question 4

An entrepreneur can take on a new client who will pay $5,000. The explicit cost for the project is $1,000. To complete the project, the entrepreneur must give up working on an alternative project that has a 50% chance of earning $6,000 and a 50% chance of earning $0. What is the correct decision based on marginal analysis?

  1. Take the client, because the marginal benefit of $5,000 is greater than the explicit marginal cost of $1,000.
  2. Do not take the client, because the marginal benefit of $5,000 is less than the potential earning of $6,000 from the alternative.
  3. Take the client, because the marginal benefit of $5,000 is greater than the total marginal cost of $4,000. (correct answer)
  4. Do not take the client, because the total marginal cost of $7,000 is greater than the marginal benefit of $5,000.
Explanation: Marginal analysis requires including all costs, including opportunity costs. The marginal benefit (MB) is the $5,000 payment. The marginal cost (MC) is the sum of explicit costs and opportunity costs. The explicit cost is $1,000. The opportunity cost is the expected value of the alternative project: (0.5 * $6,000) + (0.5 * $0) = $3,000. Total MC = $1,000 + $3,000 = 4,000.SinceMB(4,000. Since MB (5,000) > MC ($4,000), the entrepreneur should take the client.

Question 5

A government agency is funding a public health campaign. They find that spending the first million dollars saves 100 lives, the second million saves an additional 50 lives, and the third million saves an additional 10 lives. If the agency, facing a limited budget, decides to spend exactly $2 million, what can be inferred about their marginal analysis?

  1. The agency determined that the value of saving 150 lives was greater than the total cost of $2 million.
  2. The marginal benefit of saving 50 additional lives was deemed greater than or equal to the program's marginal cost, while the benefit of saving 10 more lives was not. (correct answer)
  3. The agency calculated that the average cost per life saved was lowest at the $2 million spending level.
  4. The agency stopped funding because the marginal number of lives saved began to diminish after the first million dollars.
Explanation: The decision to stop at a certain point implies a comparison at the margin. Stopping at $2 million means the marginal benefit of the second million (saving 50 lives) was judged to be worthwhile (MB ≥ MC), but the marginal benefit of the third million (saving 10 lives) was not (MB < MC). Option A discusses total benefit, C discusses average cost, and D incorrectly states that diminishing marginal benefit alone is a reason to stop.

Question 6

A factory pollutes a river. An environmental agency determines that the marginal cost to the factory of reducing pollution rises with each additional unit of abatement, while the marginal benefit to society of that abatement falls. The economically efficient level of pollution reduction occurs where:

  1. the total social benefit of a clean river is maximized, regardless of the cost to the factory.
  2. the factory's total cost of pollution abatement is minimized, ensuring its financial viability.
  3. all pollution is eliminated, as any amount of pollution represents a negative externality.
  4. the marginal cost of the last unit of pollution reduced equals its marginal benefit to society. (correct answer)
Explanation: The efficient level of any activity, including pollution abatement, is where the marginal benefit equals the marginal cost (MB=MC). Reducing pollution beyond this point would mean the cost to society (in terms of abatement expense) would be greater than the benefit (cleaner water). Reducing it less would mean society is forgoing opportunities to achieve benefits that are greater than the costs. Maximizing total benefit or minimizing total cost (A, B) leads to inefficient extremes (100% or 0% abatement).

Question 7

A city government has already spent $4 billion building a new subway line and requires an additional $3 billion to finish it. The expected future benefit of the completed line is $6 billion. However, a new report shows that the project's total cost of $7 billion will exceed its total benefit of $6 billion. What should the city do?

  1. Finish the line, because the marginal benefit of completion (6billion)isgreaterthanthemarginalcosttocomplete(6 billion) is greater than the marginal cost to complete (3 billion). (correct answer)
  2. Abandon the project, because the total cost (7billion)isgreaterthanthetotalbenefit(7 billion) is greater than the total benefit (6 billion), creating a net loss.
  3. Finish the line, because abandoning it would mean wasting the $4 billion that has already been spent on construction.
  4. Abandon the project, because the additional cost to finish is more than 50% of the amount already spent.
Explanation: This is a sunk cost problem. The 4billionalreadyspentisirrelevanttothedecisionmovingforward.Thecitymustcomparethemarginalcosttofinish(4 billion already spent is irrelevant to the decision moving forward. The city must compare the marginal cost to finish (3 billion) with the marginal benefit of finishing ($6 billion). Since the marginal benefit is greater than the marginal cost, the project should be completed. Options B and C represent the sunk cost fallacy, where past costs inappropriately influence a current decision.

Question 8

A company can invest in a new machine that costs $10,000. The machine is expected to increase total revenues by $15,000 and requires $3,000 in additional labor and materials to operate. The company's accountant notes that the average return on all existing investments is 25%. What is the correct application of the marginal decision rule?

  1. Invest, because the marginal revenue of $15,000 is greater than the marginal cost of the machine, which is $10,000.
  2. Do not invest, because the net return of $2,000 is only a 20% return on the machine cost, which is below the company's average return.
  3. Invest, because the marginal revenue of $15,000 is greater than the total marginal costs of $13,000. (correct answer)
  4. Do not invest, because the total marginal cost of $13,000 is greater than the cost of the machine itself.
Explanation: The marginal benefit is the increase in total revenue, which is 15,000.Themarginalcostisthesumofalladditionalcostsrequiredtogetthatbenefit,whichincludesthemachine(15,000. The marginal cost is the sum of all additional costs required to get that benefit, which includes the machine (10,000) and the labor/materials ($3,000), for a total of 13,000.SinceMB(13,000. Since MB (15,000) > MC ($13,000), the investment should be made. Comparing the return to an average (B) is incorrect, and comparing partial costs and benefits (A, D) is an incomplete analysis.

Question 9

A movie theater offers a promotion: buy a large popcorn for $8 and get unlimited free refills. A moviegoer buys the popcorn and has already finished their first bucket. The decision of whether to get a second bucket (a refill) should be based on which comparison?

  1. Comparing the benefit of the second bucket to the original $8 cost to see if the purchase was worthwhile in total.
  2. Comparing the benefit of the second bucket to the average cost of $4 per bucket to determine if it meets a value threshold.
  3. Comparing the total benefit of two buckets to the total cost of $8 to maximize the value of the promotion.
  4. Comparing the marginal benefit of the second bucket to its marginal cost, which is effectively zero plus any inconvenience. (correct answer)
Explanation: The $8 price is a sunk cost once the initial purchase is made. For the decision to get a refill, the marginal monetary cost is zero. Therefore, the decision hinges on whether the marginal benefit (the enjoyment of another bucket of popcorn) is greater than the marginal non-monetary cost (e.g., the inconvenience of getting up, the discomfort of eating too much). All other options incorrectly use total or average costs, or incorporate the sunk cost into the marginal decision.

Question 10

A firm's production process exhibits diminishing marginal returns. The firm is currently producing a quantity where the market price is greater than its marginal cost. Assuming the firm wants to maximize profits, which of the following statements is correct?

  1. The firm should decrease its output to the point where its average total cost is minimized.
  2. The firm should increase its output because the revenue from selling an additional unit exceeds the cost of producing it. (correct answer)
  3. The firm should maintain its current level of output because it is already earning a profit on the last unit produced.
  4. The firm should shut down if the market price is not high enough to cover its average fixed costs.
Explanation: For a price-taking firm, the market price is the marginal revenue (MR). The profit-maximization rule is to produce where MR = MC. If Price (MR) > MC, it means the firm can increase its profit by producing and selling at least one more unit. Therefore, the firm should increase its output. While it is earning a profit on the last unit (C), it is not maximizing its total profit until it expands production to the point where MR = MC.

Question 11

A monopolist firm is producing 100 units of a good. At this level, the marginal revenue from the 100th unit is $10, the marginal cost of the 100th unit is $8, and the average total cost is $7. To maximize profit, what action should the firm take?

  1. Decrease production, because the marginal revenue is decreasing and will soon be less than the marginal cost.
  2. Keep production at 100 units, because the firm is already profitable as marginal revenue exceeds average total cost.
  3. Increase production, because at the current level of output, the marginal revenue is greater than the marginal cost. (correct answer)
  4. Keep production at 100 units, because the marginal cost of $8 is greater than the average total cost of $7.
Explanation: The rule for profit maximization is to produce up to the quantity where marginal revenue equals marginal cost (MR=MC). At 100 units, MR (10)>MC(10) > MC (8). This means that producing and selling one more unit will add more to revenue than it adds to cost, thus increasing total profit. The firm should continue to increase production until MR falls to the level of MC. The average total cost is irrelevant to this marginal decision.

Question 12

A law firm hires a new associate at a salary of $120,000. With the new associate, the firm's total annual revenue is expected to increase from $2,000,000 to $2,150,000. The average revenue per lawyer at the firm will decrease with this new hire. Based on a marginal analysis, should the firm have hired the associate?

  1. No, because the average revenue per lawyer decreases, indicating diminishing returns and lower overall efficiency.
  2. The decision cannot be determined without knowing the firm's total costs and profitability before the hire.
  3. Yes, because the firm's total revenue of $2,150,000 is significantly higher than the new associate's salary.
  4. Yes, because the marginal revenue generated by the associate (150,000)isgreaterthantheirmarginalcost(150,000) is greater than their marginal cost (120,000). (correct answer)
Explanation: The decision to hire should be based on a comparison of marginal revenue and marginal cost. The marginal cost is the associate's salary, $120,000. The marginal revenue is the increase in total revenue, which is $2,150,000 - $2,000,000 = 150,000.SinceMB(150,000. Since MB (150k) > MC ($120k), the decision is profitable at the margin. A focus on falling average revenue (A) is a common error; firms should make decisions based on marginal, not average, values.

Question 13

A freelance writer can take on an additional assignment that pays $500. The writer estimates it will take 10 hours of work. The writer has other work they could do, but they value their leisure time at $30 per hour. Based on the marginal decision rule, under which condition should the writer accept the assignment?

  1. Only if the marginal benefit of $500 is greater than the marginal cost of $300, which is the value of the forgone leisure. (correct answer)
  2. The writer should always accept, as the assignment provides a positive monetary payment of $500.
  3. The writer should not accept, because the payment of $50 per hour is only slightly higher than their value of leisure.
  4. Only if the total income from all assignments is greater than the total value of all of their potential leisure time.
Explanation: The decision requires comparing the marginal benefit to the marginal cost. The marginal benefit is the payment for the assignment, $500. The marginal cost is the opportunity cost of the writer's time. Since the next best alternative is leisure valued at $30/hour, the total opportunity cost for the 10-hour assignment is 10 hours * $30/hour = 300.Thewritershouldacceptbecausethemarginalbenefit(300. The writer should accept because the marginal benefit (500) exceeds the marginal cost ($300).

Question 14

A software company has spent $500,000 developing a new application and requires an additional $100,000 to complete it. However, a competitor has just launched a similar product, causing the expected sales revenue from the new application to fall from $1,000,000 to $300,000. What is the most rational decision for the company based on the marginal decision rule?

  1. Abandon the project, because the total cost of $600,000 will be greater than the sales revenue of $300,000, resulting in a loss.
  2. Complete the project, because the marginal revenue of $300,000 is greater than the marginal cost to complete it, which is $100,000. (correct answer)
  3. Complete the project, because the company must recover some of the $500,000 that has already been spent on development.
  4. Abandon the project, because the expected revenue has fallen by more than the amount already invested in the project.
Explanation: The economically rational decision depends on comparing the marginal benefit and marginal cost of completing the project. The $500,000 already spent is a sunk cost and should be ignored. The marginal cost to complete the project is $100,000. The marginal benefit is the expected revenue from the completed project, which is 300,000.Sincethemarginalbenefit(300,000. Since the marginal benefit (300,000) exceeds the marginal cost ($100,000), the company should complete the project.

Question 15

A farmer finds that using 1 ton of fertilizer increases crop yield by 100 bushels. Using a 2nd ton increases yield by an additional 80 bushels. The price of a bushel of crops is $5, and the price of a ton of fertilizer is $450. If the farmer has already applied 1 ton of fertilizer, what is the marginal benefit and marginal cost of applying the 2nd ton?

  1. MB = $500, MC = $900
  2. MB = $400, MC = $450 (correct answer)
  3. MB = $900, MC = $900
  4. MB = $400, MC = $900
Explanation: The marginal benefit of the second ton is the additional revenue it generates. This is the additional yield (80 bushels) times the price per bushel ($5), which equals $400. The marginal cost is the cost of one additional ton of fertilizer, which is $450. The costs of the first ton and the total yield are not relevant for the marginal decision about the second ton. Since MB < MC, the farmer should not apply the second ton.

Question 16

A student has a major exam in two days and is deciding whether to spend the next hour sleeping or studying. Which of the following represents the most direct application of the marginal decision rule to this choice?

  1. Calculating the total hours slept versus total hours studied during the week to ensure they are balanced.
  2. Considering the tuition cost for the course to determine the high value of studying for the exam.
  3. Comparing the expected improvement in exam performance from one more hour of studying to the expected improvement in focus from one more hour of sleep. (correct answer)
  4. Assuming that studying for an exam is always more beneficial than sleeping, as it directly impacts the grade.
Explanation: The marginal decision rule requires comparing the marginal benefit and marginal cost of a choice. Here, the choice is how to spend the next hour. The marginal benefit of studying is the expected grade improvement. The marginal cost of studying is the opportunity cost, which is the marginal benefit of the next best alternative: sleeping. The benefit of sleeping is improved focus and well-being. Therefore, the student must compare these two marginal benefits.

Question 17

An employee is paid $25 per hour and has the option to work overtime. The employee values their first hour of evening leisure at $20, the second at $30, and the third at $40. The employee chooses to work exactly one hour of overtime. This decision implies that the:

  1. marginal benefit of a second hour of leisure (30)wasgreaterthanitsmarginalcost(30) was greater than its marginal cost (25 in forgone wages). (correct answer)
  2. employee is irrational because the benefit of the first hour of leisure ($20) was less than the wage.
  3. total benefit of three hours of leisure (90)isgreaterthanthetotalpayforthreehoursofovertime(90) is greater than the total pay for three hours of overtime (75).
  4. marginal cost of working the first hour of overtime (forgone leisure of 20)wasgreaterthanitsbenefit(20) was greater than its benefit (25 wage).
Explanation: The marginal cost of taking an hour of leisure is the forgone wage of $25. The decision to stop working after one hour means the employee is about to take their second hour of the evening as leisure. For this to be the optimal choice, the marginal benefit of that hour of leisure must be greater than or equal to its marginal cost. The MB of the second leisure hour is $30, and the MC is $25. Since $30 > 25,theemployeechoosesleisure.Thisexplainsthestoppingpoint.DisincorrectbecausetheMBofworking(25, the employee chooses leisure. This explains the stopping point. D is incorrect because the MB of working (25) was greater than the MC ($20), which is why they worked the first hour.

Question 18

A consumer continues to purchase additional units of a good until the consumer surplus from the very last unit purchased is zero. Which of the following must be true at this consumption level?

  1. The total consumer surplus from all units purchased must also be zero.
  2. The consumer receives no additional satisfaction or utility from consuming the last unit.
  3. The marginal benefit the consumer receives from the last unit is equal to the price they paid for it. (correct answer)
  4. The marginal cost of producing the last unit was equal to the price the consumer paid for it.
Explanation: Consumer surplus on a single unit is defined as the marginal benefit (what the consumer is willing to pay) minus the marginal cost (the price paid). If the consumer surplus on the last unit is zero, then Marginal Benefit - Price = 0. This implies that the Marginal Benefit equals the Price. The consumer still gets utility from the unit (B is wrong), and total consumer surplus is likely positive from earlier units (A is wrong). Producer cost (D) is not part of the consumer's calculation.