If demand remains constant at any changes in price of commodity then the elasticity of demand for that commodity will be ........
Answer & explanation
Correct answer: option 1
The correct answer is Option (1) → Zero
Price elasticity of demand is the percentage change in quantity demanded divided by the percentage change in price. If demand stays the same at any price, the top of this ratio is zero. So the elasticity is zero, and the demand curve is vertical.
Option (1) Zero — Correct. The quantity demanded does not respond to price at all.
Option (2) One — Incorrect. Quantity would change by the same percentage as the price.
Option (3) Between one and zero — Incorrect. Quantity would change, but by a smaller percentage than the price. Such demand is inelastic.
Option (4) Infinite — Incorrect. The demand curve would be horizontal. At any other price, quantity demanded drops to zero.
NCERT (2026-27): “Constant Elasticity Demand Curve The elasticity of demand on different points on a linear demand curve is different varying from 0 to ∞. But sometimes, the demand curves can be such that the elasticity of demand remains constant throughout. Consider, for example, a vertical demand curve as the one depicted in Figure 2.20(a). Whatever be the price, the demand is given at the level q. A price never leads to a change in the demand for such a demand curve and |eD| is always 0. Therefore, a vertical demand curve is perfectly inelastic. Figure 2.20 (b) depics a horizontal demand curve, where market price remains constant at P, whatever be the level of demand for the commodity. At any other price, quantity demanded drops to zero and therefore ed = ∞. A horizontal demand curve is perfectly elastic.… …Figure 2.20(c) depicts a demand curve which has the shape of a rectangular hyperbola. This demand curve has a property that a percentage change in price along the demand curve always leads to equal percentage change in quantity. Therefore, |eD| = 1 at every point on this demand curve. This demand curve is called the unitary elastic demand curve.”
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