Practice a College Board-style free response question on Basic Economic Concepts. Write your response, then reveal the model answer to see exactly what earns each point.
Suppose two countries, Alpha and Beta, each have resources that can be used to produce only two goods: textiles and machinery. Using all of its resources, each country can produce the maximum combinations shown below.
Country
Max Textiles (units)
Max Machinery (units)
Alpha
60
30
Beta
40
40
A
Calculate Alpha's opportunity cost of producing one unit of machinery, in terms of textiles. Show your work.
✓ Model answer (earns the point)
Alpha can produce a maximum of 60 textiles OR 30 machinery. Giving up all textile production (60 units) to produce 30 units of machinery means each unit of machinery costs 60/30 = 2 units of textiles.
Why it scores: Shows the calculation (60 textiles ÷ 30 machinery) and states the correct numerical answer with units (2 textiles per unit of machinery). A correct answer without showing the ratio calculation may not earn full credit.
B
Determine which country has the comparative advantage in producing machinery. Justify your answer using opportunity cost.
✓ Model answer (earns the point)
Beta has the comparative advantage in machinery. Alpha's opportunity cost of one unit of machinery is 2 textiles (from Part A). Beta's opportunity cost of one unit of machinery is 40/40 = 1 textile. Since Beta's opportunity cost (1 textile) is lower than Alpha's (2 textiles), Beta should specialize in machinery.
Why it scores: Calculates Beta's opportunity cost, explicitly compares it to Alpha's, and correctly identifies the country with the lower opportunity cost. Simply naming a country without the opportunity cost comparison would not earn the point.
C
Suppose Alpha and Beta specialize according to comparative advantage and agree to trade at a rate of 1 unit of machinery for 1.5 units of textiles. Explain why this rate of trade is mutually beneficial for both countries.
✓ Model answer (earns the point)
This trade rate is mutually beneficial because 1.5 textiles per machinery falls between each country's own opportunity cost of machinery — Alpha's domestic opportunity cost is 2 textiles per machinery, and Beta's is 1 textile per machinery. Because Alpha can obtain machinery through trade for only 1.5 textiles instead of giving up 2 textiles domestically, trading is cheaper than producing machinery itself. Beta, meanwhile, can sell machinery for 1.5 textiles even though it only cost Beta 1 textile to produce — earning more in trade than its production cost. Since both countries get a better deal through trade than through producing the good domestically, both gain from trading at this rate.
Why it scores: Identifies that the trade rate sits between both countries' opportunity costs AND explains, for each country specifically, why the rate beats their own domestic opportunity cost. Just saying "both countries benefit" without the opportunity-cost comparison would not earn the point.
How to score points on AP Microeconomics FRQs
Always show your calculation, not just the answer. Opportunity cost and comparative advantage problems almost always require you to show the ratio or division that produced your number.
Name specific economics, not vague concepts. "Lower opportunity cost" scores higher than "better at it." "Comparative advantage" is sharper than "an advantage."
Answer the verb in the prompt. "Calculate" needs a number with work shown. "Determine and justify" needs an answer PLUS the reasoning that supports it. "Explain" needs a causal chain, not just a restatement.
For trade questions, compare the rate to BOTH countries' opportunity costs. A trade rate is mutually beneficial only if it falls between the two opportunity costs — show that explicitly.
Be concise but complete. 2–4 sentences per part is usually enough. Avoid filler — every sentence should add something a grader can mark.