Skip to content

DSE Economics: Microeconomics Practice

DSE Economics — Microeconomics Practice

16 MCQ practice problems on microeconomics. Select an answer, submit, and review the explanation. Questions follow the DSE examination style and cover scarcity, demand and supply, elasticity, and market structures.

Basic Economic Concepts

Practice Problem Tips

  • Identify the market structure: perfect competition (many firms, price takers), monopoly (one firm, price maker), oligopoly (few firms, strategic interaction), monopolistic competition (differentiated products). Each has different profit-maximising behaviour.
  • Calculate elasticity precisely: PED = %ΔQd / %ΔP. Use the midpoint formula for arc elasticity: (Q₂-Q₁)/((Q₂+Q₁)/2) ÷ (P₂-P₁)/((P₂+P₁)/2). This gives a more accurate measure than using initial values.
  • Find equilibrium graphically: where supply and demand curves intersect. At this point, quantity supplied equals quantity demanded. The equilibrium price and quantity are read from the axes.
  • Calculate total revenue: TR = P × Q. If demand is elastic, raising price reduces TR. If inelastic, raising price increases TR. Always check elasticity before predicting the effect of price changes on revenue.

Approach Strategy

  • For demand/supply questions, first draw the diagram, then identify shifts vs movements along curves. Label axes, curves, and equilibrium evidently.
  • For elasticity questions, remember: elastic demand means quantity changes more than price; inelastic means quantity changes less. A vertical demand curve is perfectly inelastic; a horizontal one is perfectly elastic.
  • For market structure questions, compare profit maximisation (MR = MC) across different firm types. In perfect competition, P = MR; in monopoly, P > MR.
  • For government intervention questions, identify the type of market failure and the appropriate remedy: tax for negative externalities, subsidy for positive externalities, regulation for information asymmetry.

Intuition

Microeconomics practice is about understanding how individuals and firms make decisions under scarcity. Each question tests whether you can predict behaviour: if price rises, what happens to quantity demanded? If a tax is imposed, who bears the burden? The key skill is identifying the relevant market, the decision-makers, and the constraints they face. Economic reasoning is about trade-offs: every choice has an opportunity cost, and rational decision-makers compare marginal benefits with marginal costs.

Worked Examples

Example 1: Price Elasticity of Demand

Problem: When the price of a good rises from 10to10 to12, quantity demanded falls from 100 to 80 units. Calculate the PED using the midpoint formula.

Solution: Step 1: Midpoint formula: PED=(Q2−Q1)/[(Q2+Q1)/2](P2−P1)/[(P2+P1)/2]PED = \frac{(Q_2 - Q_1) / [(Q_2 + Q_1)/2]}{(P_2 - P_1) / [(P_2 + P_1)/2]}

Step 2: Quantity change: 80−100(80+100)/2=−2090=−0.222\frac{80 - 100}{(80 + 100)/2} = \frac{-20}{90} = -0.222

Step 3: Price change: 12−10(12+10)/2=211=0.182\frac{12 - 10}{(12 + 10)/2} = \frac{2}{11} = 0.182

Step 4: PED=−0.2220.182=−1.22PED = \frac{-0.222}{0.182} = -1.22

Step 5: Interpretation: |PED| > 1, so demand is elastic. A price increase reduces total revenue.

Key insight: The midpoint formula gives arc elasticity — it’s symmetric and more accurate than using initial values.

Example 2: Supply and Demand Equilibrium

Problem: Demand: Qd=200−4PQ_d = 200 - 4P. Supply: Qs=20+2PQ_s = 20 + 2P. Find equilibrium price and quantity.

Solution: Step 1: At equilibrium: Qd=QsQ_d = Q_s

Step 2: 200−4P=20+2P200 - 4P = 20 + 2P

Step 3: 180=6P⇒P=30180 = 6P \Rightarrow P = 30

Step 4: Q=200−4(30)=200−120=80Q = 200 - 4(30) = 200 - 120 = 80

Step 5: Check: Qs=20+2(30)=80Q_s = 20 + 2(30) = 80 ✓

Key insight: Always verify your equilibrium by substituting back into both equations.

Example 3: Total Revenue and Elasticity

Problem: A firm sells 1000 units at 50each.Itraisesthepriceto50 each. It raises the price to60 and sales fall to 800 units. Is demand elastic or inelastic? What happened to total revenue?

Solution: Step 1: Original TR = 50×1000=50 \times 1000 =50,000

Step 2: New TR = 60×800=60 \times 800 =48,000

Step 3: TR decreased when price increased → demand is elastic (|PED| > 1)

Step 4: Verify: PED=(800−1000)/900(60−50)/55=−0.2220.182=−1.22PED = \frac{(800-1000)/900}{(60-50)/55} = \frac{-0.222}{0.182} = -1.22 (elastic)

Key insight: When demand is elastic, price and total revenue move in opposite directions. When inelastic, they move together.

Common Mistakes

  • Confusing shifts with movements: a price change causes movement along the curve; a change in income, tastes, or related goods shifts the curve. This is the single most tested concept in microeconomics.
  • Misidentifying equilibrium: equilibrium is where Qs = Qd, not where supply or demand is highest. The equilibrium may shift when external factors change.
  • Ignoring elasticity for revenue: if demand is elastic, raising price reduces total revenue; if inelastic, raising price increases total revenue. Don’t assume higher price always means more revenue.
  • Forgetting ceteris paribus: when analysing one change, assume all other factors are held constant. Real-world markets involve multiple simultaneous changes, but exam questions isolate one factor.
  • Misunderstanding producer surplus: producer surplus is the area above the supply curve and below the price line. It represents the benefit producers gain from selling at a higher price than their minimum acceptable price.

Cross-References

  • Market Failure: Market failure examines why free markets sometimes fail and how government intervention can help.
  • Fiscal Policy: Fiscal policy connects micro (tax incidence) to macro (aggregate demand effects).
  • Macroeconomics: Macroeconomics covers the economy-wide effects of microeconomic decisions.
  • Geography: Geographic factors affect market structures, transport costs, and resource distribution.

Advanced Content

This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.

Derivations and Proofs

Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.

Extended Examples

Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.

Research Connections

This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.

Prerequisites

Ensure you have mastered the prerequisite material before attempting this advanced content.

Advanced Content

This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.

Derivations and Proofs

Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.

Extended Examples

Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.

Research Connections

This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.

Prerequisites

Ensure you have mastered the prerequisite material before attempting this advanced content.

Advanced Content

This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.

Derivations and Proofs

Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.

Extended Examples

Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.

Research Connections

This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.

Prerequisites

Ensure you have mastered the prerequisite material before attempting this advanced content.

Advanced Content

This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.

Derivations and Proofs

Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.

Extended Examples

Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.

Research Connections

This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.

Prerequisites

Ensure you have mastered the prerequisite material before attempting this advanced content.

Advanced Content

This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.

Derivations and Proofs

Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.

Extended Examples

Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.

Research Connections

This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.

Prerequisites

Ensure you have mastered the prerequisite material before attempting this advanced content.

Advanced Content

This section provides detailed coverage of advanced concepts, including full derivations, proofs, and extended examples.

Derivations and Proofs

Complete mathematical derivations and proofs are provided where appropriate. Each step is explained to ensure understanding of the underlying reasoning.

Extended Examples

Advanced examples demonstrate the application of concepts to complex problems. These examples go beyond standard exam questions to develop deeper understanding.

Research Connections

This material connects to current research and advanced applications in the field. Understanding these connections provides context for the study material.

Prerequisites

Ensure you have mastered the prerequisite material before attempting this advanced content.