AP Microeconomics — Unit 3: Production, Cost, and the Perfect Competition Model

What AP Microeconomics Unit 3 covers

The College Board Course and Exam Description breaks Unit 3 into 7 topics:

1. 3.1 The Production Function
2. 3.2 Short-Run Production Costs
3. 3.3 Long-Run Production Costs
4. 3.4 Types of Profit
5. 3.5 Profit Maximization
6. 3.6 Firms' Short-Run Decisions to Produce and Long-Run Decisions to Enter or Exit a Market
7. 3.7 Perfect Competition

AP Microeconomics Unit 3 practice questions

• You have 3 ovens and can hire as many bakers as you want. What does the production function map out as you keep adding bakers?

  It maps inputs (labor, capital) to output produced. It shows how much a firm can produce as it adds workers or resources.

• 5 workers make 100 units. You hire a 6th and output climbs to 115. Your manager points at the new total of 115 to judge the hire. Which number ACTUALLY tells you what that 6th worker added — and what is it here?

  Marginal product: 15 = (115 − 100) ÷ 1 worker. MP = change in output ÷ change in workers; the total of 115 hides the real contribution.

• Worker #2 adds 15 units, but #3 adds only 12 and #4 just 7. A friend blames 'lazy new hires.' What's the real economic law at work here?

  The law of diminishing marginal returns. Add more workers to a FIXED amount of capital (same machines, same floor space) and each new worker's marginal product eventually falls — not because they're lazy, but because they're crowding the same fixed resources.

• Your bakery closes for the month. The landlord still wants $5,000. You stop buying flour. Which cost is which — and why does the distinction matter for your short-run decision?

  Fixed costs don't change with output; variable costs do. FC = rent, insurance (paid even at zero output); VC = materials, hourly wages. TC = FC + VC.

• At 10 units, total cost is $100. At 11 units, it's $112. A student divides $112 by 11 and says the 11th unit cost $10.18. What did they calculate by mistake — and what's the real cost of that 11th unit?

  They calculated ATC ($112 ÷ 11), not MC. Marginal cost is the CHANGE: ΔTC ÷ ΔQ = ($112 − $100) ÷ 1 = $12. The 11th unit added $12, even though the average per unit is only $10.18.

• A firm's fixed cost is $200, no matter what. As it cranks out more and more units, which per-unit cost is GUARANTEED to keep shrinking toward zero — and why can't it ever rise?

  Average fixed cost (AFC = FC ÷ Q), spread ever thinner. The fixed $200 is split over more units, so AFC only ever falls toward zero.

• MC slices through both the ATC and the AVC curves. A classmate sketches it cutting both at the same output. What's the one spot on each curve MC must pass through — and why can't it be the same output for both?

  MC crosses each curve at its MINIMUM. But AVC bottoms out at a lower output than ATC (ATC sits higher because it carries AFC), so MC hits AVC's min first, then ATC's min later. Different curves, different bottoms, different crossing points.

• Why does specialization initially cause marginal cost to FALL?

  Early hires specialize and divide labor, so they're more productive. Rising MP means each extra unit costs less, so MC falls — until diminishing returns hit.

+ 27 more AP Microeconomics cards in the app.

Key terms in Unit 3

These 5 terms show up in the Unit 3 cards. Each one links to its definition in the AP Microeconomics key-term reference.

• equilibrium
• monopolistic competition
• monopoly
• oligopoly
• perfect competition