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Class 9 The Price Puzzle: What Drives the Market: cheat sheet
CBSE Social Science. Demand and supply and what shifts them, substitutes and complements, market equilibrium, price ceilings and floors, monopoly and market regulators.
Key ideas
- Demand is the quantity buyers are willing and able to buy at a price; by the Law of Demand, a higher price means less is demanded.
- By the Law of Supply, a higher price means sellers offer more.
- Besides price, demand depends on income, tastes and the prices of substitutes and complements; supply depends on technology, the number of sellers and expectations.
- At the equilibrium price quantity demanded equals quantity supplied: a price above it leaves a surplus, a price below it a shortage.
- A price ceiling is a legal maximum (some medicines) and a price floor a legal minimum (a minimum wage); a ceiling set too low can cause shortages.
- A monopoly is a single seller with no close substitutes, so it is regulated.
- Regulators keep markets fair: the RBI for banking, TRAI for telecom and SEBI for the share market.
Remember
| Law of Demand | price ↑ → quantity demanded ↓ |
| Law of Supply | price ↑ → quantity supplied ↑ |
| Equilibrium | quantity demanded = quantity supplied |
| Substitutes and complements | tea and coffee; a car and petrol |
| Ceiling and floor | a legal maximum price; a legal minimum price |
| Diminishing marginal utility | each extra unit gives less extra satisfaction |
Watch out
- Swapping a price ceiling (maximum) and a price floor (minimum).
- Mixing up substitutes (used instead of each other) and complements (used together).
- Saying a surplus pushes prices up: a surplus makes sellers cut prices, a shortage pushes them up.
Worked example
A Goa hotel charges ₹1,500 in the off-season, ₹6,000 on a December Saturday and ₹27,000 on New Year’s Eve. (a) How many times the off-season price is the New Year price? (b) If the December rate is cut by 20%, what is it? (c) Why do prices change like this?
Working: 27,000 ÷ 1,500; 20% off 6,000
Answer: (a) 18 times (b) ₹4,800 (c) Demand rises at peak times and falls off-season, so prices move with demand.
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