Perfect Competition Practice Questions

8 representative multiple-choice questions on perfect competition for AP Microeconomics, drawn from our 15-question bank for this module. Work through each one, then open “Show answer” for the correct choice and an explanation. For scored, timed practice across the full bank, take a full practice test.

1. 1. A perfectly competitive firm maximizes profit by producing where:

   • A. Price = ATC
   • B. MR = MC, which simplifies to P = MC
   • C. Total revenue is maximized
   • D. ATC is at its minimum
   Show answer

   Correct answer: B. MR = MC, which simplifies to P = MC

   In perfect competition, MR equals the market price because the firm is a price taker. So MR = MC becomes P = MC. The firm produces the quantity where its marginal cost curve crosses the horizontal price line. (C) is wrong because maximizing total revenue means selling as much as possible while ignoring costs. A firm could have enormous revenue and still hemorrhage money on every unit.

2. 2. A competitive firm should shut down in the short run when:

   • A. Price is below ATC
   • B. Price is below AVC
   • C. Economic profit is zero
   • D. Marginal cost is rising
   Show answer

   Correct answer: B. Price is below AVC

   Shutdown happens when P < minimum AVC. At that point, the firm can't even cover variable costs, so producing makes the loss worse than simply closing and paying fixed costs. (A) is the trap answer on virtually every practice exam. A firm below ATC but above AVC should keep producing. It's losing money, but it loses *less* by staying open.

3. 3. If market demand increases in a perfectly competitive market, what happens in the short run?

   • A. Existing firms earn economic profit as market price rises
   • B. Firms immediately exit the market
   • C. The market price stays the same because firms are price takers
   • D. Each firm's MC curve shifts to the right
   Show answer

   Correct answer: A. Existing firms earn economic profit as market price rises

   A rightward demand shift raises the equilibrium price. At the higher price, each firm produces more (moving up along its MC curve) and earns economic profit because P now exceeds ATC. In the long run, entry would erode these profits. (C) is wrong because while each firm *takes* the market price, the market price itself still changes when demand shifts. The firm takes whatever the new equilibrium price happens to be.

4. 4. Allocative efficiency in perfect competition means:

   • A. Firms produce at the lowest point on their ATC curves
   • B. Price equals marginal cost, so resources go to their highest-valued use
   • C. All firms earn positive economic profit
   • D. Government regulates output to the socially optimal level
   Show answer

   Correct answer: B. Price equals marginal cost, so resources go to their highest-valued use

   P = MC is allocative efficiency. The price consumers pay for the last unit equals what it cost to produce. No reshuffling of resources could improve total welfare. (A) describes productive efficiency, which is producing at the lowest ATC. Related concepts, but they're distinct, and confusing them on the AP exam costs points.

5. 5. Which of the following is NOT a characteristic of perfect competition?

   • A. Many buyers and sellers
   • B. Firms are price makers
   • C. Identical (homogeneous) products
   • D. Free entry and exit in the long run
   Show answer

   Correct answer: B. Firms are price makers

   Competitive firms are price takers, not price makers. No individual firm can set or influence the market price. Price-making power belongs to monopolists and other imperfectly competitive firms. The other three options (many participants, identical products, free entry/exit) are all genuine features of perfect competition.

6. 6. In long-run equilibrium under perfect competition, firms earn zero economic profit. This means:

   • A. Firms are not covering their costs and will eventually go bankrupt
   • B. Firms earn no accounting profit whatsoever
   • C. Firms earn a normal rate of return that exactly covers all opportunity costs, including the cost of capital
   • D. Total revenue equals total variable cost
   Show answer

   Correct answer: C. Firms earn a normal rate of return that exactly covers all opportunity costs, including the cost of capital

   Zero economic profit = all explicit costs (wages, rent, materials) covered AND all implicit costs (the owner's foregone salary, the return capital could earn elsewhere) covered. The firm is doing fine. It just has no reason to enter or leave the industry. (A) is wrong because zero economic profit is not failure; every cost including opportunity cost is met. (B) confuses economic and accounting profit. A firm earning zero economic profit typically still reports positive accounting profit on its income statement. (D) describes the shutdown point where TR = TVC, a completely different concept.

7. 7. A perfectly competitive firm produces where P = MC = $20. At this output, ATC = $15 and AVC = $11. The firm's economic profit per unit and total economic profit at Q = 500 units are:

   • A. Profit per unit = $5, total profit = $2,500
   • B. Profit per unit = $9, total profit = $4,500
   • C. Profit per unit = $20, total profit = $10,000
   • D. Profit per unit = $0, because the firm is in long-run equilibrium
   Show answer

   Correct answer: A. Profit per unit = $5, total profit = $2,500

   Profit per unit = P − ATC = $20 − $15 = $5. Total = $5 × 500 = $2,500. Straightforward. (B) subtracts AVC ($11) from price ($20) to get $9, but that measures the contribution margin over variable costs, not economic profit. You have to measure against ATC, which includes fixed costs. (C) uses the entire price as profit, ignoring costs altogether. (D) assumes long-run equilibrium, but P ($20) exceeds ATC ($15), so the firm is earning positive economic profit and entry hasn't driven the price down yet.

8. 8. A competitive firm's marginal cost curve is MC = 4 + 2Q, and its minimum AVC is $8 (occurring at Q = 2). If the market price is $6, the firm will:

   • A. Produce 1 unit because P = MC at Q = 1
   • B. Produce 2 units to minimize average variable cost
   • C. Shut down and produce zero units because price is below minimum AVC
   • D. Produce where P = ATC instead
   Show answer

   Correct answer: C. Shut down and produce zero units because price is below minimum AVC

   P ($6) < minimum AVC ($8). Shutdown. Every unit produced makes the loss worse than simply absorbing fixed costs and producing nothing. (A) is a clever trap. Technically P does equal MC at Q = 1 ($6 = 4 + 2(1)), but the P = MC rule only applies in the region above minimum AVC. Below that threshold, the firm doesn't produce at all. (B) is wrong because operating at minimum AVC doesn't help when revenue per unit ($6) is still below that minimum ($8). (D) is wrong because competitive firms use P = MC, not P = ATC, and besides, the shutdown condition makes the question moot.