Skip to content

CMA Foundation · Fundamentals of Business Economics and Management

Theory of Demand and Supply for CMA Foundation

Demand and supply theory explains how price is set in a market. Demand is what buyers will purchase at each price. Supply is what sellers will offer at each price. Price settles where the two are equal, called equilibrium. You solve questions by spotting which curve moves, which way, and what happens to price and quantity.

What this chapter covers

This chapter in Paper 4 (Section A, Economics) explains how buyers and sellers decide, and how their decisions together fix the price and quantity traded. It starts with demand: what drives it, the law of demand, its exceptions, and how to separate a movement along a curve from a shift of the curve. Then it measures how strongly buyers react to price changes through elasticity.

The second half mirrors the first for supply: determinants, the law of supply and elasticity of supply. The chapter ends by putting both sides together in market equilibrium, where you find the price at which quantity demanded equals quantity supplied and see what happens when either curve shifts.

This chapter is the base for the rest of the economics section. Later topics such as production and cost, market forms and price determination under competition, monopoly and other structures all assume you know how demand, supply and equilibrium work. Learn it well once and many later questions become easier.

Paper 4 is fully objective and Section A is Economics, so a core chapter like this feeds many questions, both direct definitions and short calculations. The questions are usually quick to answer if your concepts are clear: identify the shift, apply the elasticity formula, or find the equilibrium. There is no negative marking, so even a doubtful question deserves an informed guess. Strong marks here also build the understanding you need for the chapters that follow.

Theory of Demand and Supply: topics in the order to study them

  1. 1Meaning and Determinants of DemandStart here because every later idea in the chapter builds on what demand is and what moves it.
  2. 2Law of Demand and Its ExceptionsOnce you know the determinants, the law shows the price-quantity link when all else is held constant.
  3. 3Change in Quantity Demanded vs Change in DemandThis separates a price-driven movement along the curve from a shift caused by other factors, a favourite MCQ area.
  4. 4Elasticity of DemandElasticity measures the strength of the response to price, so it needs the law and the movement idea first.
  5. 5Meaning and Determinants of SupplyNow repeat the same approach on the seller's side while the demand logic is fresh.
  6. 6Law of Supply and Elasticity of SupplyThis pairs the supply law with its responsiveness measure, mirroring what you did for demand.
  7. 7Market Equilibrium and Price DeterminationFinish with equilibrium because it needs both demand and supply and tests everything together.

How to prepare Theory of Demand and Supply

Aim to understand each idea in one line, then practise it on short MCQs. Keep sessions short so they work on a phone.

  1. Write one-line meanings for demand, supply, law of demand, law of supply and equilibrium, and learn them in your own words.
  2. List the determinants of demand and of supply side by side. Mark which ones shift the curve and which one (own price) only moves along it.
  3. Draw each curve by hand with a small table of prices and quantities. Practise showing a shift right and a shift left.
  4. Learn the elasticity formula: Ed = % change in quantity demanded ÷ % change in price. Practise with simple numbers and remember the categories: elastic, inelastic, unitary, perfectly elastic and perfectly inelastic.
  5. Solve equilibrium questions by setting quantity demanded equal to quantity supplied, then put the price back into either equation to get quantity.
  6. Attempt timed MCQs in sets of 10, reviewing every wrong answer and noting whether the error was a concept or a calculation slip.
  7. Revise the exceptions to the law of demand and the cases that shift curves one day before the exam.

Common mistakes in Theory of Demand and Supply

  • Calling a price-driven change a shift in demand

    Fix: Ask: did the good's own price change? If yes, it is a movement along the curve. If another factor changed, the curve shifts.

  • Forgetting the 'other things constant' condition in the law of demand

    Fix: Always attach the condition when stating the law, and remember that income, tastes and related prices are held fixed.

  • Mixing up elastic and inelastic values

    Fix: Link greater than 1 with a big quantity response (elastic) and less than 1 with a small response (inelastic).

  • Using the wrong base when finding percentage changes

    Fix: Use the formula given in the question or the standard one consistently, and write the change and the original value before dividing.

  • Shifting the wrong curve in an equilibrium question

    Fix: Identify who is affected, such as a rise in buyers' income (demand) or a fall in input cost (supply), then shift only that curve.

  • Treating exceptions to the law of demand as the normal rule

    Fix: Remember the law holds in general, and the exceptions are specific cases you can name and recognise from their features.

Last-day revision: Theory of Demand and Supply

  • Demand is the quantity buyers are willing and able to buy at each price in a given period.
  • Law of demand: other things constant, a lower price raises quantity demanded, and a higher price lowers it.
  • A change in the good's own price causes a movement along the curve; a change in any other determinant shifts the curve.
  • An increase in demand shifts the curve right; a decrease shifts it left.
  • Ed = % change in quantity demanded ÷ % change in price, usually read as a positive number.
  • Ed > 1 is elastic, Ed < 1 is inelastic, Ed = 1 is unitary elastic.
  • Supply rises with price: a higher price gives a higher quantity supplied, other things constant.
  • A change in input costs, technology or taxes shifts the supply curve; own price moves along it.
  • Equilibrium is where quantity demanded equals quantity supplied, giving the market price.
  • If price is above equilibrium there is excess supply, and price tends to fall; if below, there is excess demand, and price tends to rise.
  • If demand rises with supply unchanged, equilibrium price and quantity both rise.
  • If supply rises with demand unchanged, equilibrium price falls and quantity rises.

Theory of Demand and Supply practice questions

Theory of Demand and Supply in other exams

The same ground in other exams, if you are preparing for more than one or want another angle on it.

Theory of Demand and Supply: frequently asked questions

How should I study Theory of Demand and Supply for CMA Foundation?

Study demand first, then elasticity, then supply, and finish with equilibrium. Draw the curves by hand and practise short MCQs after each topic. This keeps the ideas connected.

Is this chapter mostly theory or calculation?

It is a mix. Many questions test definitions and the difference between movement and shift, while others need a simple elasticity or equilibrium calculation. Keep the numbers simple and the method fixed.

What is the quickest way to handle equilibrium questions?

Set quantity demanded equal to quantity supplied and solve for price. Then substitute that price into either equation to get quantity. For shift questions, decide which curve moves and in which direction.

Should I attempt every question even if I am unsure?

Yes. The paper has no negative marking, so you lose nothing by answering. Eliminate options you know are wrong first, then pick the best remaining one.