On a straight-line demand curve AB, a point R divides the curve such that the lower segment RB measures 60 uni

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Q. On a straight-line demand curve AB, a point R divides the curve such that the lower segment RB measures 60 units of length and the upper segment RA measures 20 units. Find the price elasticity of demand at point R by the geometric method.

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Geometric-method formula. At any point on a straight-line demand curve extended to both axes,

E_p = \frac{\text{lower segment}}{\text{upper segment}} = \frac{RB}{RA}

Substitute the given lengths. $RB = 60$ , $RA = 20$ .

E_p = \frac{60}{20} = 3

Classify. Since $E_p = 3 > 1$ , demand at R is relatively elastic — in fact strongly so. Because the lower segment is longer than the upper, R lies above the midpoint of the curve (nearer the Y-axis), exactly where elasticity exceeds 1. …

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Same / Similar Concept — real previous-year questions on the same or a closely similar concept, not this exact question.

CBSE 2023Set ANNUAL1 markMCQ
$Q. The demand for necessaries is :$
(a) Elastic
(b) Inelastic
(c) Unitary elastic
(d) Perfectly elastic
›Reveal solutionSolution

Necessaries must be consumed regardless of price, so their quantity demanded changes very little with price — their demand is inelastic. Answer: (b) Inelastic.

Price elasticity of demand measures the responsiveness of quantity demanded to a change in price. Demand is elastic when a small price change causes a large change in quantity, and inelastic when even a large price change causes only a small change in quantity.

…

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CBSE 2023Set ANNUAL1 mark
$Q. Examine the correctness of the following statement and correct it if incorrect, without changing the underlined portion : The shape of Unitary elastic demand curve is Vertical.$
›Reveal solutionSolution
The statement is incorrect; a unitary elastic demand curve is a rectangular hyperbola, not vertical. Correct statement: 'The shape of unitary elastic demand curve is a rectangular hyperbola.'

The shape of a demand curve reflects its price elasticity:

Unitary elastic demand (elasticity exactly equal to one) means a given percentage change in price causes an equal percentage change in quantity demanded, so total expenditure stays constant at every price. A curve that keeps price times quantity constant everywhere is a rectangular hyperbola.

A vertical demand curve represents perfectly inelastic demand (elasticity = 0) — quantity demanded does not change at all when price changes.

A horizontal demand curve represents perfectly elastic demand (elasticity = infinity). …
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CBSE 2019Set ANNUAL1 markMCQ
$Q. The shape of a perfectly elastic demand curve is$
(a) Downward sloping
(b) Vertical
(c) Horizontal
(d) Rectangular hyperbola
›Reveal solutionSolution
The correct answer is (c) Horizontal.

The shape of a demand curve reflects its price elasticity — a key topic in CHSE Odisha +2 Business Economics (aligned with the NCERT/CBSE curriculum).

Downward sloping (a) is the shape of a normal demand curve with finite elasticity, not the perfectly elastic case.

Vertical (b) represents perfectly inelastic demand (elasticity = 0), where quantity does not change with price.

Horizontal (c) represents perfectly elastic demand (elasticity = infinity): at the ruling price consumers buy any amount, but a tiny rise in price reduces demand to zero. …
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←Previous questionExample 3 — A shopkeeper finds that when he charges ₹50 per unit he sells 200 unit…→Next questionExample 5 — The demand function for a good is Qd = 100 - 2P. Find the price elasti…

Q.On a straight-line demand curve AB, a point R divides the curve such that the lower segment RB measures 60 units of length and the upper segment RA measures 20 units. Find the price elasticity of demand at point R by the geometric method.

Concept understanding — Price Elasticity of Demand and Its Measurement

Q.On a straight-line demand curve AB, a point R divides the curve such that the lower segment RB measures 60 units of length and the upper segment RA measures 20 units. Find the price elasticity of demand at point R by the geometric method.

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