What is meant by market demand? Explain the derivation of market demand curve with the help of a diagram. **OR

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Q. What is meant by market demand? Explain the derivation of market demand curve with the help of a diagram. OR Why does the demand curve shift? Clarify shift in the demand curve and movement along the demand curve.

Rajasthan RbseRBSE Rajasthan Senior Secondary (Class-12) Commerce Board 2025Subjective· 4mImportance★★★★★est

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Concept understanding — Market Demand Aggregation

Market Demand Aggregation

The Everyday Intuition

Imagine you run a small stall selling samosas near a school. You don't care about what one particular student wants — you care about what all the students together want. If 50 students each want 2 samosas, you need to make 100. That's aggregation: adding up individual wants to see the total demand you face.

Now scale this up. A market isn't one person's wish list — it's the sum of everyone's wish lists at every possible price. Market demand aggregation is simply the process of adding together the quantities demanded by all individual buyers at each price level.

The Precise Meaning

Market demand is the total quantity of a good that all consumers in a market are willing and able to buy at various prices, over a given time period.

The key idea: we don't just add up quantities at one price — we add up entire demand schedules (or curves) across all consumers.

Q_m(P) = \sum_{i=1}^{n} q_i(P)

How It Works: A Simple Example

Suppose a market has only two consumers, A and B.

Price (₹)	A's demand (units)	B's demand (units)	Market demand (units)
10	5	3	8
8	8	6	14
6	12	9	21
4	17	13	30

At each price, we simply add horizontally: $Q_m = q_A + q_B$ . This is called horizontal summation of individual demand curves.

Why It Matters

For firms: A business doesn't produce for one customer — it produces for the market. Knowing market demand tells a firm how much to produce at each price, and how revenue will change if price changes.

For policymakers: Taxes, subsidies, and price controls affect everyone. Market demand helps predict total consumption changes. For example, if the government imposes a ₹2 tax on samosas, market demand tells us how many fewer samosas will be bought in total.

For understanding markets: The market demand curve is what interacts with market supply to determine equilibrium price and quantity. Without aggregation, we can't analyse how markets actually work.

The Law of Demand Holds for Market Demand Too …

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Market demand = total quantity demanded by all consumers at each price; the market demand curve is the horizontal summation of individual demand curves.

In the RBSE/CBSE Class-12 consumer-behaviour chapter, market demand for a good is the total quantity that all consumers in the market together are willing and able to buy at each possible price, other things remaining constant.

Derivation (horizontal summation):

The market demand curve is obtained by horizontally adding up the individual demand curves — i.e. at every given price, we add the quantities demanded by each individual consumer.

Numerical illustration (two consumers A and B):

Price (₹)	Demand of A (units)	Demand of B (units)	Market Demand (A + B)
10	2	3	5
8	4	5	9
6	6	7	13

How to draw it:

Axes: X-axis = quantity; Y-axis = price.
Draw each consumer's downward-sloping demand curve (DA and DB). …

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The single most important determinant of consumer demand is the good's own price.

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$Q. If the demand curves of two consumers are d1(P) = 20 - P and d2(P) = 15 - P respectively, find out the market demand curve.$
›Reveal solutionSolution
Adding the two individual demand curves gives market demand D(P) = 35 - 2P.

The market demand curve is the horizontal summation of individual demand curves — at each price we add the quantities each consumer demands.

Given:

Consumer 1: d1(P) = 20 - P

Consumer 2: d2(P) = 15 - P

Market demand D(P) = d1(P) + d2(P) = (20 - P) + (15 - P) = 35 - 2P.

…
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Demand requires desire for the good, a given price, and willingness plus ability to spend — all of these together — so the answer is (D).

A mere wish to have a commodity is not demand. Effective demand in economics requires: (i) a desire to consume the good, (ii) reference to a given price at which it is wanted, and (iii) the willingness and ability (purchasing power) to pay that price. Only when desire is backed by wi …

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$Q. Which of the following is a determinant of demand for a good? (A) Price of good (B) Consumer taste (C) Consumer preference (D) All of these$
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Price of the good, consumer taste and consumer preference are all determinants of demand, so (D) is correct.

In the RBSE/CBSE Class-12 consumer-behaviour chapter, the quantity demanded of a good depends on several factors:

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The demand curve generally slopes downward from left to right, so the answer is (C).

In the BSEB Inter Class-12 Economics syllabus, the law of demand states that, other things remaining constant, a fall in price raises quantity demanded and a rise in price lowers it — price and quantity demanded are inversely related. Plotted with price on the y-axis and quantity on the x-axis, this inverse relation gives a demand curve that **slopes down …

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$Q. For a change in which of the following, there is no change in demand? (A) Change in price (B) Change in income (C) Change in taste and fashion (D) None of these$
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A change in the good's own price causes a change in quantity demanded, not a change in demand, so the answer is (A).

In the BSEB Inter Class-12 Economics syllabus, a careful distinction is made between change in quantity demanded (a movement along the same demand curve, caused only by a change in the good's own price) and change in demand (a shift of the whole demand curve, caused by changes in income, tastes/fashion, prices of related goods, etc.). Therefore a change in the good's own price does not s …

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A demand curve shows the relationship between the quantity demanded of a good and its price, so the answer is (d).

A demand curve is a graphical representation of the demand schedule; it shows the relationship between the price of a commodity and the quantity demanded of it, other things remaining constant. Price is taken on the vertical axis and quantity demanded on the horizontal axis. Because of the i …

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The demand curve for a normal good is downward-sloping, i.e. it has a negative slope, so the answer is (b).

For a normal good the Law of Demand applies: as price falls, quantity demanded rises, and as price rises, quantity demanded falls. This inverse relationship means that when we plot price on the vertical axis and quantity on the horizontal axis, the demand …

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The demand function is X = f(P) — option (C).

The demand function shows the functional relationship between the quantity demanded of a commodity (X) and its own price (P), assuming other determinants (income, tastes, prices of related goods) stay constant. Hence X = f(P). H …

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$Q. Fill in the blank:$
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›Reveal solutionSolution

The total demand of all consumers is market demand.

Market demand is obtained by horizontally summing the individual demands of all consumers in the market at each price. It shows the total quantity of a commodity that all buyers together are willing to purchas …

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Q.What is meant by market demand? Explain the derivation of market demand curve with the help of a diagram. OR Why does the demand curve shift? Clarify shift in the demand curve and movement along the demand curve.

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