EconomicsICSE Class 10 · Demand and Supply

Supply and the Law of Supply: Schedule and Curve (ICSE Class 10 Economics)

Updated 17 October 2026 · Fact-checked

Supply is the quantity of a commodity a seller is willing and able to offer for sale at a given price in a given period. The law of supply says that, other things remaining the same, quantity supplied rises when price rises and falls when price falls, so the supply curve slopes upward. Market supply is the sum of the supplies of all sellers at each price.

Understand Supply and the Law of Supply

Meaning. Supply is the part of the stock that a seller actually brings to the market at a price. Stock is the total quantity the seller has. A farmer with 500 kg of tomatoes (stock) may offer only 300 kg at ₹20 per kg (supply).

Law of supply. Other things remaining constant, the quantity supplied of a commodity rises when its price rises and falls when its price falls. The relation between price and quantity supplied is direct.

Supply schedule and curve.

Price per unit (₹)	Firm X (units)	Firm Y (units)	Market supply (units)
10	20	10	30
20	40	30	70
30	60	50	110
40	80	70	150

Plot price on the Y-axis and quantity on the X-axis. The curve SS slopes upward from left to right. The market supply curve is the horizontal sum of individual curves and lies to the right.

Why supply rises with price. A higher price means a higher profit per unit, so sellers wish to supply more. At a higher price, sellers can also cover a higher marginal cost, so they are willing to offer more from their stock or output.

Assumptions. Prices of inputs, technology, taxes and subsidies, number of firms and the goals of firms are constant. (If the number of firms changes, market supply shifts; this is not a movement along the curve.)

Demand versus supply. Demand is from the buyer, shows an inverse relation with price and has a downward curve; supply is from the seller, shows a direct relation and has an upward curve.

Supply and the Law of Supply: key facts

Supply (meaning): Quantity offered for sale
At a price
In a period
Willing and able
Law of supply: Price up, quantity supplied up
Direct relation
Ceteris paribus
Market supply: Sum of all sellers' quantities at each price
Stock and supply: Stock = total quantity held | Supply = part of the stock offered at a price

How to answer Supply and the Law of Supply questions

The structure is the same as for demand, with the relation reversed.

1State the law with "other things remaining constant".
2Add individual supplies row by row for market supply.
3Plot price on the Y-axis and quantity on the X-axis; the curve rises to the right.
4Distinguish stock from supply when asked.
5Name the assumptions: input prices, technology, taxes, number of firms.

Supply and the Law of Supply in real life

The idea, met in an everyday situation. Answer the question in your own words, then compare with the model answer. The one-line hook is what to remember.

A fruit seller's mangoes

Suppose a seller holds 200 kg of mangoes. At ₹60 per kg he offers 80 kg for sale and at ₹90 per kg he offers 140 kg.

What are the stock, supply at each price, and the percentage change in supply?

Try it first, then show the solutionSolution

Stock is 200 kg.
Supply is 80 kg at ₹60 and 140 kg at ₹90.
Change = (140 − 80) ÷ 80 × 100 = 75% when price rises by (90 − 60) ÷ 60 × 100 = 50%.

Answer: Stock 200 kg; supply 80 kg and 140 kg; supply increases by 75% when the price rises by 50%.

Memory hook: Higher price, more to the market.

Tricks to remember Supply and the Law of Supply

Short memory aids. Say each one aloud once, then use it on a question the same day.

Seller smiles at high price
High price means more supply.
Use it when: Law of supply.
Stock is the store; supply is the shop window
Only the part displayed is supply.
Use it when: Stock versus supply.
Demand falls, supply rises
Price up: demand down, supply up.
Use it when: Comparing the two laws.

Supply and the Law of Supply: solved examples

Ordered from board level to HOTS. Try each one before you open the solution.

Example 1: Slope · 1 mark · MCQBoard level

The supply curve normally slopes:
(a) upward from left to right
(b) downward from left to right
(c) vertically
(d) horizontally

Try it first, then show the solutionSolution

Direct relation with price.

Answer: (a)

Example 2: Market supply · 2 marks · Short answerBoard level

At ₹25 Firm A supplies 40 units, Firm B 35 units and Firm C 25 units. Find market supply. If at ₹35 each supplies 10 units more, find the new market supply. (2 marks)

Try it first, then show the solutionSolution

At ₹25: 40 + 35 + 25 = 100 units.
At ₹35: 100 + 3 × 10 = 130 units (check: 50 + 45 + 35 = 130).

Answer: 100 units; 130 units.

Example 3: Stock and supply · 3 marks · Short answerHarder board level

A potter has 500 pots in stock. At ₹80 per pot he offers 300 for sale; at ₹100 he offers 400. Find the supply at each price and the change in supply in per cent. (3 marks)

Try it first, then show the solutionSolution

Supply is 300 at ₹80 and 400 at ₹100; the rest is held back in stock.
Change = (400 − 300) ÷ 300 × 100 = 33.3% (33⅓%).
Price change = (100 − 80) ÷ 80 × 100 = 25%.

Answer: Supply rises by 33.3% when the price rises by 25%.

Example 4: Draw and describe · 3 marks · Short answerHarder board level

Using the market supply schedule in the concept section, explain how you would draw the supply curve and what its shape shows. (3 marks)

Try it first, then show the solutionSolution

Plot (30, ₹10), (70, ₹20), (110, ₹30), (150, ₹40) with quantity on the X-axis and price on the Y-axis.
Join the points; the line rises to the right.
This shows the direct relation: each ₹10 rise adds 40 units.

Answer: Upward-sloping curve; supply increases by 40 units for every ₹10 rise.

Example 5: Compare demand and supply · 4 marks · Long answerHOTS / competency

State any four differences between the law of demand and the law of supply. (4 marks)

Try it first, then show the solutionSolution

Relation: inverse for demand; direct for supply.
Curve: downward for demand; upward for supply.
Who: buyers for demand; sellers for supply.
Reason: demand is based on utility and income; supply is based on profit and cost.

Answer: Relation, slope, side of the market and basis.

Where students lose marks in Supply and the Law of Supply

The slips examiners see most often, and what to write instead.

Mistake: Treating stock as supply
Terms mixed.
Wrong working
Supply = all goods the seller has.
Right working
Supply = the part of stock offered at a price.
Do this: Always define both.
Usually costs: 1 mark.
Mistake: Drawing a downward supply curve
Copying the demand diagram.
Wrong working
SS slopes down.
Right working
SS slopes upward to the right.
Do this: Rehearse both diagrams.
Usually costs: 1 mark.
Mistake: Not stating the assumptions
Law is incomplete.
Wrong working
Quantity supplied rises with price.
Right working
Other things constant: cost of inputs, technology, taxes.
Do this: Say "other things remaining constant".
Usually costs: 1 mark.

Exam tips

Draw SS upward and label axes.
Define stock and supply in one line each.
Add the quantities across rows in market schedules.

Practice questions on Supply and the Law of Supply

Write each answer on paper first. Open the hint only if you are stuck, and the answer only when you have finished.

Q1 · 1 mark · MCQBoard level
The law of supply shows a ____ relation between price and quantity supplied.
(a) inverse
(b) direct
(c) no
(d) circular
Hint
Higher price, more supply.
Answer
(b)
Q2 · 2 marks · Short answerBoard level
Define supply. How is it different from stock? (2 marks)
Hint
Part of stock.
Answer
Supply is the quantity offered for sale at a price in a period; stock is the total quantity with the seller, of which only a part is supply.
Q3 · 3 marks · Short answerHarder board level
Prepare a market supply schedule from these data: price ₹5, ₹10, ₹15; firm P: 10, 20, 30 units; firm Q: 5, 15, 25 units. (3 marks)
Hint
Add rows.
Answer
₹5: 15 units; ₹10: 35 units; ₹15: 55 units.
Q4 · 3 marks · Short answerHarder board level
Why does a higher price lead to a larger quantity supplied? Give two reasons. (3 marks)
Hint
Profit.
Answer
A higher price raises the profit per unit, so sellers want to supply more; it also lets sellers cover a higher marginal cost, so they are willing to offer more from their stock or output.
Q5 · 3 marks · Short answerHOTS / competency
Suppose the supply of a good rises from 80 to 100 units when the price rises from ₹20 to ₹24. Find the per cent change in supply and in price, and say whether this is a movement or a shift and why. (3 marks)
Hint
Own price change.
Answer
Supply: (100 − 80) ÷ 80 × 100 = 25%. Price: (24 − 20) ÷ 20 × 100 = 20%. It is a movement along the same curve (extension of supply) because it is caused by the commodity's own price.

Test your recall

Answer in your head or on paper first, then open the card. Pulling an answer out of memory makes it stick far better than re-reading.

1.Relation between price and supply?Show answer
Direct.
2.Slope of supply curve?Show answer
Upward.
3.Market supply?Show answer
Sum of all firms' supply at each price.
4.Stock versus supply?Show answer
Supply is the part of stock offered.
5.Who determines supply?Show answer
Sellers.

Supply and the Law of Supply: frequently asked questions

What is the law of supply?

Other things constant, a higher price brings a larger quantity supplied.

What is the shape of the supply curve?

It slopes upward from left to right.

What is market supply?

The total quantity supplied by all sellers at each price.